Pineapple House
11-21-2002, 10:22 PM
Note, this was not written by me, so I deserve no credit for what was said in this.
INTRODUCTION
Clownfish are one of the easiest tropical marine aquarium fish to breed. Unlike many of the other tropical marine aquarium fish, clownfish regularly spawn in the marine aquarium. Furthermore clownfish have relatively large eggs and larvae which makes raising them a somewhat easier task as the larvae are able to eat easily cultured live foods.
The purpose of this article is to convey the information that I have found and learned over the last few months while I have been raising clownfish. Part 1 of this article will deal with tank setup for breeding clownfish, obtaining a pair of clownfish, feeding, spawning, and larval tank design. Part 2 will deal with the large area of larval rearing and culturing live feeds.
All the information in this article is a compilation of information from the last 5 years that I have kept clownfish and all the books and articles that I have read. A complete reference list of clownfish related articles will be compiled at the end part 2 of this article.
There are a few very important steps to breeding clownfish. These include setting up the tank, choosing the broodstock, feeding, spawning and raising the larvae. These points will all be discussed in detail below.
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SETTING UP THE TANK
A clownfish spawning tank should be as large as possible, and preferably not smaller than 100 litres. If the purpose of the tank is to solely breed clownfish then it would be wise to avoid putting any other fish in the tank. Small non aggressive fish can be added, however once the fish start spawning anything that comes toward them is viewed as a threat and chased away.
As a rule the more natural a tank is the more at home the fish will feel and the more likely they will be to spawn. This is not to say that a tank with a flowerpot and a thin layer of coral sand wont produce results. Its just that the more relaxed and stress free the fish feel, the sooner they will spawn and the healthier the eggs will be.
An ideal tank would be a 3x2x2 filled with live rock, a layer of coral sand on the bottom, a few live rocks, a nice anemone, bright lighting and good filtration, preferably an efficient protein skimmer. As the biological load of the tank would just be the clownfish, the live rock and protein skimmer would handle the ammonia and organic materials from the fish. A trickle filter could be used providing regular water changes are performed to keep the nitrates low enough for the anemone to do well.
In nature the clownfish spawning is linked to the lunar cycle. It is generally not practical to artificially simulate the lunar cycle in anaquarium. It is important however that the lights are connected to a timer so that the fish receive a regular day/night lighting cycle. This regular cycle of day night is all that is needed.
An anemone is generally not required to breed clownfish however it certainly makes the task much easier in the long run. In fact clownfish have been known to spawn on clay pots, clam shells and even the aquarium glass in the absence of an anemone. An added benefit of having an anemone is that it may release compounds that help protect the eggs or even may chemically with apparent immunity that clownish have with the anemone.
The key to your clownfish home is that it be STRESS FREE! That means good water quality, no aggressive tank mates and an anemone.
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CHOOSING THE BROODSTOCK
There are three basic ways to obtaining a pair of clownfish. These include: 1) to purchase a naturally mated pair captured from the wild, 2) to buy a small group of at least four fish and 3) to buy two fish of greatly differing size.
1) Obtaining a naturally mated pair of clownfish is always the best option. This is because the pair of fish will be a naturally mated pair from the time you put them into the aquarium and will not have to go through the territorial and aggressive struggles that happen in an aquarium when fish are first introduced. Also the fish will not view each other as aggressive rivals as they are a pair. The best news however is that by introducing a mated pair to the aquarium spawning will commence much sooner than by the other two methods.
2) Buying a small group of clownfish, preferably from different sources, is the next best option. This is because it gives the clowns a chance to form a hierarchical structure in the tank with the two most dominant fish naturally pairing off. It also lowers the chance of the other clownfish becoming overly stressed due to aggression from the dominant fish as the aggression is spread out over a number of individuals. This option will produce a pair but it will take longer for them to start spawning than if they were a mated pair as soon as they were added to the aquarium.
3) Putting two fish of differing size in together is an extreme way of obtaining a pair of fish. The reason for this is that often the larger fish will be very aggressive toward its own kind and if there is only one other clownfish then that aggression can cause the other fish to become very stressed and more prone to disease. This problem will persist until the larger more dominant female fish accepts the smaller male. This task may take anywhere from a few days to several weeks.
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FEEDING
Once the tank is setup and the fish have been introduced its time to start feeding them. Believe it or not feeding is probably the most important aspect of whether you will have success with breeding clownfish or not. If your broodstock do not attain the correct amounts and types of nutrients then they will not be able to develop good quality eggs. If the eggs are of bad quality then no matter how hard you try, you will not have much success in raising the larvae.
The key to nutrition in clownfish is a mixed diet of fresh raw seafood and vegetable matter. A good diet for clownfish includes, mussels, prawns, squid and green vegetables. These can be mixed together and made into a mash and frozen or can be just fed separately. The amounts of food to feed the clownfish depends on their size however it is always best to feed small amounts at regular intervals. Remember clownfish will take large bits of food to their anemone so its a good idea to feed them small bits!
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SPAWNING
Once the clownfish have settled into their new home, anywhere from 1 to 12 months, spawning will commence. The first indication of possible spawning are when the male clownfish dances up and down in front of the female. The male will dance in a head up fashion and will thrust toward the female. This is known as the clownfish waggle. This is a pretty lose indicator but generally means that spawning will happen soon! The next indication is when the male and often the female also start to clean a patch of rock near the foot of the anemone. This is a good indication that spawning will commence within a day or two. The last indicator of spawning is the sight of the both the male and female clownfish’ s genital tubes. This usually means that the fish will be spawning within the next few hours.
Spawning starts when the female swims over the cleared patch of rock and deposits a small line of eggs with her ovipositor. The male follows shortly after and fertilisers them. The process of laying eggs often takes from 2 to 3 hours. The eggs look like little capsules about 2 to 3 mm long and 1 mm wide. If the adults have been fed well then the eggs should be a bright orange colour. During this time the clownfish (Amphiprion clarkii) may lay up to 600 eggs. More often than not however the number of eggs starts out small, around 200, and increases with each spawn and as the female increases in size. Once the fish have started spawning they re likely to repeat at intervals of around 12 to 18 days.
The eggs usually take from 6 to 15 days to hatch depending on temperature. One day prior to hatching the larvae within the eggs develop a silvery colour around their eye. This is the time when you must make a decision. Either you leave the eggs in the tank to hatch and you remove the larvae or one day prior to hatching you remove the rock upon which the eggs were laid.
If the eggs are to be removed on the rock then it is important that the eggs are kept under water at all times. The water in which the eggs will be placed must have also been taken from the spawning tank as small differences in water quality parameters may damage the eggs. Once the eggs are in the larval rearing tank then they must be provided with sufficient water current to properly oxygenate them. The easiest way to do this is via an airstone that produces course bubbles. All that is then required is to remove the rock after hatching.
If the eggs are to be left in the main aquarium then some planning will have to be made. To make things easier the lights can be turned off earlier as the larvae will hatch within two hours of darkness. Once the lights have switched off all circulation to and within the tank must be ceased. This will ensure that the larvae are not sucked up and damaged by pumps and water currents. After the pumps have been turned off and the tank is still its time to wait! The eggs will hatch in waves and as the larvae hatch they will swim to the surface. Once at least a quarter of the eggs have hatched its time to use the torch (flashlight). The torch is shone in the water, from above, and used to concentrate the larvae into a small group. Once this is done the larvae can either be siphoned into the larval rearing tank with airline tubing or dipped out with small plastic cups or containers. This is done repetitively until all the larvae are caught.
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LARVAL REAING TANK
Clownfish larvae can be reared in many different sorts of containers and tanks. Old 2ft aquariums can be used however I have found that circular tanks give much better results. This I because rectangular or square tanks have corners and with no strong currents to thoroughly mix the water dead spots develop in the corners. In these dead spots pathogenic bacteria thrive and canmultiply, especially is old food collects in the corners. This in the end will cause the death of many clownfish larvae. With round tanks there is no such problem as there are no corners and it is very easy to get the water to circulate in a circular fashion.
An ideal larval rearing tank is a round plastic or fibreglass tank with a water holding capacity of between 50 and 150 litres. The tanks can be setup as 1) having a filter and recirculating water or 2) stand alone and just using airstones and partial water changes.
1) The ideal setup for clownfish larvae is to have a central standpipe in the round tank and have around the standpipe a mesh screen of between 100 and 300 microns. The different mesh sizes are used for different sized live feeds such as rotifers and artemia. Water overflows into a sump where there is some sort of biological filtration and mechanical filtration. A low volume pump then pumps water back to the tank at a very slow rate, just enough to cause the water to slowly circulate and keep the larvae moving. An airstone may be required in the centre of the tank along the side of the screen to ensure that it does not block up. This system closely matches the natural environment where the larvae are found, where they are drifting in the surface waters.
2) The second option is to have a round tank with only aeration provided. This setup is much easier to prepare however water quality can become a problem unless regular water changes are performed to reduce ammonia levels. A further problem also develops in that it is much harder to flush excess live food out of the tank.
The larval rearing tank should receive the same lighting cycle as the main tank. It preferably should have its own light and timer. The reason for having a light is that the larvae are visual predators and require light to hunt for their live food prey. The type of lighting is not critical and can be from any source of light, ie fluorescent, metal halide, incandescent etc.
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INTRODUCTION TO LARVAL REARING
Once you have managed to get this far you better take a rest because the hardest part is yet to come! Larval rearing is perhaps the most difficult aspect that is holding back the aquaculture of many of our tropical marine aquarium fish. This is mainly because of the largely unknown dietary requirements of the different larval fishes. Clownfish however are not all that that hard to rear. Infact they are comparable in difficulty to many of the harder to breed freshwater fishes. The only things that make it more difficult are that live food is required and so time must be put into culturing both the live food and the clownfish larvae.
In larval rearing of clownfish there is a very important aspect to consider as there appears to be two distinct larval size classes in clownfish. In a few species of clownfish the larvae are able to eat Artemia naupilii first off while the majority of the clownfish species produce larvae that can only eat rotifers first off.. Species of clowns which are known to produce "larger" larvae include Amphiprion clarkii and Amphiprion frenantus. This is not a hard and fast rule by any means and does not mean that your Percula clown larvae wont eat Artemia first off.. With all clowns its best to make provisions to produce rotifers and feed then along with Artemia as the more variety of food the larvae have the better.
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LARVAL PERIOD
The clownfish have a larval period of between 10 and 20 days. From the time the larvae hatch out of their eggs they are larvae. Once they change their behaviour from swimming on the top to swimming on the bottom and develop the adult striped colouration they are no longer larvae. The time at which they develop their adult colouration and look like miniature adults is called metamorphosis. From metamorphosis onwards the clownfish actively swim on the bottom of the tank and in nature this is the time when they seek out an anemone.
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LARVAL FEEDS
Clownfish larvae will eat both Artemia and rotifers. They can also be weaned onto finely powdered dry foods as a supplements to the live feeds.
The reason clownfish require the first food to be live is to do with their development. When the larvae first start feeding they larvae do not posses any digestive enzymes. By eating a live food they basically get a fully packaged first meal containing both the nutritional requirements need and the live foods own enzymes - which in turn break the food down. Clownfish larvae have also adapted to hunting for food by sight. Which means that it wont attack a non living food particle in the water. It requires movement to act as a stimulus to catch its food. After a few days however clownfish can be weaned onto small amounts of dry powered foods.
There is no risk of larvae overeating on either rotifers or Artemia. Larvae will eat as much as they need. They will not burst either. This is just a fallacy. Accounts of larvae dying from over eating are normally always to from intestinal blockage, ingestion of air bubbles or bacterial problems.
Artemia are small crustaceans that are hatched from small brown cysts. The cysts can be purchased from aquarium shops and aquaculture supply houses. The Artemia are hatched by placing the cysts into saltwater and aerating it. 18 to 24 hours later the Artemia have hatched out. The Artemia are then separated from the empty hatched cysts and are fed to the fish. Hatching is a very easy procedure however there is one serious concern with introducing empty hatched cysts along with the Artemia to the larvae. This is because the hatched out of cysts of the Artemia will often be eaten by the larvae and will cause intestinal blockage. Thedanger becomes increasingly worse with time because the larvae only start eating the empty cysts once they have become proficient at catching Artemia, which may take a few days, by which time many cysts have accumulated in the tank.. This problem can be solved however by purchasing "decapsulated cysts" or decapsulating them yourself.. The procedure is as follows:
a) place the required quantity of Brine Shrimp eggs in a glass or plastic bottle/beaker and add from 200 to 400 mL of tap water. Place this in the fridge for one hour.
b) after one hour remove the eggs and pour in sodium hypochlorite (liquid pool chlorine) at a ratio of 1:1. That is to say add at least as much chlorine as water that you have in the container. After addition of chlorine immediately start stirring the mixture. After a minute or two the eggs will start to change colour, first to a gray, then white and finally orange. When the eggs start to turn orange the decapsulation process is complete. From start to finish the whole process should take from between 3 - 5 minutes.
c) once the eggs start to turn orange they must be pored into a mesh bag of around 100 m m. They should then be rinsed in clean flowing tapwater for atleast 2 minutes or until no detectable smell of chlorine.
d) the decapsulated cysts are now ready for hatching. If a large quantity of cysts has been decapsulated at once, they can be stored for a week or two in the fridge in a strong brine solution of 300 grams per litre of salt.
Rotifers unlike Artemia cannot be purchased as tins of cysts. Rotifers must be cultured along with algae, which can be very time consuming. It is beyond the scope of this article to go into the culture of rotifers and algae as that would take up a good few pages all on its own.
To culture rotifers you will need to obtain both algae and rotifers. They can both be obtained from Florida Aquafarms. Florida Aquafarms sell a rotifer and algae starter pack which contains all the info and starter cultures to get you started.
Dry powdered foods can be added after a couple of days to help reduce the burden of continually hatching and culturing live foods. These should however only be added in small quantities as any food that is not eaten will foul the water.
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LARVAL REARING
Clownfish larvae always hatch at night, usually within three hours after dark. Sometimes however a clutch of eggs my hatch over two days on consecutive nights. After hatching clownfish have a yolk sac that provides them nourishment for atleast a further twelve hours. Since they conveniently hatch at night it means that first thing in the morning live food can be added to the rearing tank. This ensures that the larvae actually get a chance to familiarise themselves with chasing and catching the live food BEFORE all their energy reserves (inside the yolk sac) are depleted. If food was only added at the time of yolk sac depletion then many larvae would die because they have to learn to catch their own food and this takes a few hours. Infact it takes a few days before the larvae become very proficient at live food capture.
For the first two days live food densities should be kept quite high. For rotifers the density should be atleast 20/mL and for Artemia atleast 5/mL. This will ensure that the larvae will have a better chance of catching their prey. During this time the larval tank must be kept very clean with the bottom siphoned of dead larvae, detritus and feces twice a day. This is important because any decaying matter on the bottom will encourage potentially harmful bacterial growth and will lower the oxygen levels and deteriorate the water quality. Water changes will also need to be performed at a rate of atleast 25% per day and not more than 50% per day. The replacement water should be of the same temperature and pH to reduce shock.
Do not worry about siphoning out the live food when changing water. It is important to add newly cultured or hatched live food every day because the nutritional value of the live food that remains in the tank will decrease very quickly. This is because in the case of the Artemia naupilii, its mouth has yet to form and it is using up its internal reserves. The artemia also grows with time and within 36 hours may be too big for the larvae to eat. The rotifer on the other hand has a mouth but it also has little nutritional valueto it. What makes a rotifer nutritional is what is in its stomach. Rotifers also have very high feeding rate and pass out what they have eaten very quickly. The larval tank doesn’t have any algae in it there is so there is no food for the rotifer to eat. Thus after the water has been changed new rotifers and or Artemia must be added.
If the larvae have begun eating and are getting enough food they will be very active and will be seen swimming until they see a rotifer or artemia. They will then stop and watch it then snake back and lurch forward at the prey. This is natural attack behaviour. The healthy larvae will appear to have a well rounded body and should be swimming in a close horizontal position. Unhealthy larvae will tend to either buzz around on the surface at a 45 degree angle or listlessly swim at 45 degrees. The unhealthy larvae will have a hollow shape and will not be rounded.
For the first two day there will be some losses of larvae. Especially if the larvae have been transferred using the siphon method. Most deaths found on the first morning can be attributed to transportation related damage. On day two there might start to be the first of the starving related deaths. These are often the larvae which have not been able to master food capture.
From day three to eight the larvae will grow very fast. The densities of live food can be reduced as the larvae have become proficient at food capture. By now the larvae that were too small to eat Artemia first off will be able to eat them. Rotifers should be maintained at 10/mL (until Artemia are being accepted by all larvae) and Artemia at 10/mL. If the larvae have been eating Artemia they will have pink stomachs. This can be checked by scooping a larvae into a glass and shining a torch from underneath.. During this time the larval tank must be kept very clean with the bottom siphoned of dead larvae, detritus and feces twice a day. Water changes will also need to be performed at a rate of atleast 25% per day and not more than 50% per day. The replacement water should be of the same temperature and pH to reduce shock.
Day eight to eleven are very dangerous days. This is the timeframe when the larvae start to look like adults and metamorphosize. During this time the larvae are more tolerant to water conditions however they can be very sensitive to fright. It is best to not siphon the bottom or make any drastic changes to the tank at this time. Artemia can still be fed at a rate of 10/mL. A few days before metamorphosis the larvae will start to develop stripes and some of the adult colours. On the day of metamorphosis the larvae can be often found sitting motionless on the bottom.. The next day they appear to be swimming on the bottom in the clownfish fashion "waggle" and with the adult colours.
Metamorphosis onwards, the hard work is over. The clownfish can now be fed Artemia few times a day and slowly weaned onto dry foods. Its best not to move the small clownfish until they have reached atleast 14 days or until all have metamorphosized. Alternatively the fish can be left in the larval tank until they have outgrown it (only if it has a filter).
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GROWTH
From time of hatch to attaining a size of 2.5 to 3cm can take as little as 12 weeks. The rate at which the young fish grow depends on the size of the tank they are in, the stocking density, the quality and quantity of food given and the temperature. A problem to consider is that dominant clownfish will grow the fastest and will suppress the growth of the fish below. This can largely overcome however by growing the fish up all together in a large tank.
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CONCLUSION
Clownfish are a fun and educational species of fish to breed. With the knowledge you gain from breeding clownfish you can start to tackle the more difficult species of marine fish.
I hope this article has convinced atleast one person to go ahead and have a go at breeding clownfishes as you will never know how good it feels to produce a tank of 60 little clowns unless you do it!
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David Bloch
HTH
PH =)
INTRODUCTION
Clownfish are one of the easiest tropical marine aquarium fish to breed. Unlike many of the other tropical marine aquarium fish, clownfish regularly spawn in the marine aquarium. Furthermore clownfish have relatively large eggs and larvae which makes raising them a somewhat easier task as the larvae are able to eat easily cultured live foods.
The purpose of this article is to convey the information that I have found and learned over the last few months while I have been raising clownfish. Part 1 of this article will deal with tank setup for breeding clownfish, obtaining a pair of clownfish, feeding, spawning, and larval tank design. Part 2 will deal with the large area of larval rearing and culturing live feeds.
All the information in this article is a compilation of information from the last 5 years that I have kept clownfish and all the books and articles that I have read. A complete reference list of clownfish related articles will be compiled at the end part 2 of this article.
There are a few very important steps to breeding clownfish. These include setting up the tank, choosing the broodstock, feeding, spawning and raising the larvae. These points will all be discussed in detail below.
*
SETTING UP THE TANK
A clownfish spawning tank should be as large as possible, and preferably not smaller than 100 litres. If the purpose of the tank is to solely breed clownfish then it would be wise to avoid putting any other fish in the tank. Small non aggressive fish can be added, however once the fish start spawning anything that comes toward them is viewed as a threat and chased away.
As a rule the more natural a tank is the more at home the fish will feel and the more likely they will be to spawn. This is not to say that a tank with a flowerpot and a thin layer of coral sand wont produce results. Its just that the more relaxed and stress free the fish feel, the sooner they will spawn and the healthier the eggs will be.
An ideal tank would be a 3x2x2 filled with live rock, a layer of coral sand on the bottom, a few live rocks, a nice anemone, bright lighting and good filtration, preferably an efficient protein skimmer. As the biological load of the tank would just be the clownfish, the live rock and protein skimmer would handle the ammonia and organic materials from the fish. A trickle filter could be used providing regular water changes are performed to keep the nitrates low enough for the anemone to do well.
In nature the clownfish spawning is linked to the lunar cycle. It is generally not practical to artificially simulate the lunar cycle in anaquarium. It is important however that the lights are connected to a timer so that the fish receive a regular day/night lighting cycle. This regular cycle of day night is all that is needed.
An anemone is generally not required to breed clownfish however it certainly makes the task much easier in the long run. In fact clownfish have been known to spawn on clay pots, clam shells and even the aquarium glass in the absence of an anemone. An added benefit of having an anemone is that it may release compounds that help protect the eggs or even may chemically with apparent immunity that clownish have with the anemone.
The key to your clownfish home is that it be STRESS FREE! That means good water quality, no aggressive tank mates and an anemone.
*
CHOOSING THE BROODSTOCK
There are three basic ways to obtaining a pair of clownfish. These include: 1) to purchase a naturally mated pair captured from the wild, 2) to buy a small group of at least four fish and 3) to buy two fish of greatly differing size.
1) Obtaining a naturally mated pair of clownfish is always the best option. This is because the pair of fish will be a naturally mated pair from the time you put them into the aquarium and will not have to go through the territorial and aggressive struggles that happen in an aquarium when fish are first introduced. Also the fish will not view each other as aggressive rivals as they are a pair. The best news however is that by introducing a mated pair to the aquarium spawning will commence much sooner than by the other two methods.
2) Buying a small group of clownfish, preferably from different sources, is the next best option. This is because it gives the clowns a chance to form a hierarchical structure in the tank with the two most dominant fish naturally pairing off. It also lowers the chance of the other clownfish becoming overly stressed due to aggression from the dominant fish as the aggression is spread out over a number of individuals. This option will produce a pair but it will take longer for them to start spawning than if they were a mated pair as soon as they were added to the aquarium.
3) Putting two fish of differing size in together is an extreme way of obtaining a pair of fish. The reason for this is that often the larger fish will be very aggressive toward its own kind and if there is only one other clownfish then that aggression can cause the other fish to become very stressed and more prone to disease. This problem will persist until the larger more dominant female fish accepts the smaller male. This task may take anywhere from a few days to several weeks.
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FEEDING
Once the tank is setup and the fish have been introduced its time to start feeding them. Believe it or not feeding is probably the most important aspect of whether you will have success with breeding clownfish or not. If your broodstock do not attain the correct amounts and types of nutrients then they will not be able to develop good quality eggs. If the eggs are of bad quality then no matter how hard you try, you will not have much success in raising the larvae.
The key to nutrition in clownfish is a mixed diet of fresh raw seafood and vegetable matter. A good diet for clownfish includes, mussels, prawns, squid and green vegetables. These can be mixed together and made into a mash and frozen or can be just fed separately. The amounts of food to feed the clownfish depends on their size however it is always best to feed small amounts at regular intervals. Remember clownfish will take large bits of food to their anemone so its a good idea to feed them small bits!
*
SPAWNING
Once the clownfish have settled into their new home, anywhere from 1 to 12 months, spawning will commence. The first indication of possible spawning are when the male clownfish dances up and down in front of the female. The male will dance in a head up fashion and will thrust toward the female. This is known as the clownfish waggle. This is a pretty lose indicator but generally means that spawning will happen soon! The next indication is when the male and often the female also start to clean a patch of rock near the foot of the anemone. This is a good indication that spawning will commence within a day or two. The last indicator of spawning is the sight of the both the male and female clownfish’ s genital tubes. This usually means that the fish will be spawning within the next few hours.
Spawning starts when the female swims over the cleared patch of rock and deposits a small line of eggs with her ovipositor. The male follows shortly after and fertilisers them. The process of laying eggs often takes from 2 to 3 hours. The eggs look like little capsules about 2 to 3 mm long and 1 mm wide. If the adults have been fed well then the eggs should be a bright orange colour. During this time the clownfish (Amphiprion clarkii) may lay up to 600 eggs. More often than not however the number of eggs starts out small, around 200, and increases with each spawn and as the female increases in size. Once the fish have started spawning they re likely to repeat at intervals of around 12 to 18 days.
The eggs usually take from 6 to 15 days to hatch depending on temperature. One day prior to hatching the larvae within the eggs develop a silvery colour around their eye. This is the time when you must make a decision. Either you leave the eggs in the tank to hatch and you remove the larvae or one day prior to hatching you remove the rock upon which the eggs were laid.
If the eggs are to be removed on the rock then it is important that the eggs are kept under water at all times. The water in which the eggs will be placed must have also been taken from the spawning tank as small differences in water quality parameters may damage the eggs. Once the eggs are in the larval rearing tank then they must be provided with sufficient water current to properly oxygenate them. The easiest way to do this is via an airstone that produces course bubbles. All that is then required is to remove the rock after hatching.
If the eggs are to be left in the main aquarium then some planning will have to be made. To make things easier the lights can be turned off earlier as the larvae will hatch within two hours of darkness. Once the lights have switched off all circulation to and within the tank must be ceased. This will ensure that the larvae are not sucked up and damaged by pumps and water currents. After the pumps have been turned off and the tank is still its time to wait! The eggs will hatch in waves and as the larvae hatch they will swim to the surface. Once at least a quarter of the eggs have hatched its time to use the torch (flashlight). The torch is shone in the water, from above, and used to concentrate the larvae into a small group. Once this is done the larvae can either be siphoned into the larval rearing tank with airline tubing or dipped out with small plastic cups or containers. This is done repetitively until all the larvae are caught.
*
LARVAL REAING TANK
Clownfish larvae can be reared in many different sorts of containers and tanks. Old 2ft aquariums can be used however I have found that circular tanks give much better results. This I because rectangular or square tanks have corners and with no strong currents to thoroughly mix the water dead spots develop in the corners. In these dead spots pathogenic bacteria thrive and canmultiply, especially is old food collects in the corners. This in the end will cause the death of many clownfish larvae. With round tanks there is no such problem as there are no corners and it is very easy to get the water to circulate in a circular fashion.
An ideal larval rearing tank is a round plastic or fibreglass tank with a water holding capacity of between 50 and 150 litres. The tanks can be setup as 1) having a filter and recirculating water or 2) stand alone and just using airstones and partial water changes.
1) The ideal setup for clownfish larvae is to have a central standpipe in the round tank and have around the standpipe a mesh screen of between 100 and 300 microns. The different mesh sizes are used for different sized live feeds such as rotifers and artemia. Water overflows into a sump where there is some sort of biological filtration and mechanical filtration. A low volume pump then pumps water back to the tank at a very slow rate, just enough to cause the water to slowly circulate and keep the larvae moving. An airstone may be required in the centre of the tank along the side of the screen to ensure that it does not block up. This system closely matches the natural environment where the larvae are found, where they are drifting in the surface waters.
2) The second option is to have a round tank with only aeration provided. This setup is much easier to prepare however water quality can become a problem unless regular water changes are performed to reduce ammonia levels. A further problem also develops in that it is much harder to flush excess live food out of the tank.
The larval rearing tank should receive the same lighting cycle as the main tank. It preferably should have its own light and timer. The reason for having a light is that the larvae are visual predators and require light to hunt for their live food prey. The type of lighting is not critical and can be from any source of light, ie fluorescent, metal halide, incandescent etc.
*
INTRODUCTION TO LARVAL REARING
Once you have managed to get this far you better take a rest because the hardest part is yet to come! Larval rearing is perhaps the most difficult aspect that is holding back the aquaculture of many of our tropical marine aquarium fish. This is mainly because of the largely unknown dietary requirements of the different larval fishes. Clownfish however are not all that that hard to rear. Infact they are comparable in difficulty to many of the harder to breed freshwater fishes. The only things that make it more difficult are that live food is required and so time must be put into culturing both the live food and the clownfish larvae.
In larval rearing of clownfish there is a very important aspect to consider as there appears to be two distinct larval size classes in clownfish. In a few species of clownfish the larvae are able to eat Artemia naupilii first off while the majority of the clownfish species produce larvae that can only eat rotifers first off.. Species of clowns which are known to produce "larger" larvae include Amphiprion clarkii and Amphiprion frenantus. This is not a hard and fast rule by any means and does not mean that your Percula clown larvae wont eat Artemia first off.. With all clowns its best to make provisions to produce rotifers and feed then along with Artemia as the more variety of food the larvae have the better.
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LARVAL PERIOD
The clownfish have a larval period of between 10 and 20 days. From the time the larvae hatch out of their eggs they are larvae. Once they change their behaviour from swimming on the top to swimming on the bottom and develop the adult striped colouration they are no longer larvae. The time at which they develop their adult colouration and look like miniature adults is called metamorphosis. From metamorphosis onwards the clownfish actively swim on the bottom of the tank and in nature this is the time when they seek out an anemone.
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LARVAL FEEDS
Clownfish larvae will eat both Artemia and rotifers. They can also be weaned onto finely powdered dry foods as a supplements to the live feeds.
The reason clownfish require the first food to be live is to do with their development. When the larvae first start feeding they larvae do not posses any digestive enzymes. By eating a live food they basically get a fully packaged first meal containing both the nutritional requirements need and the live foods own enzymes - which in turn break the food down. Clownfish larvae have also adapted to hunting for food by sight. Which means that it wont attack a non living food particle in the water. It requires movement to act as a stimulus to catch its food. After a few days however clownfish can be weaned onto small amounts of dry powered foods.
There is no risk of larvae overeating on either rotifers or Artemia. Larvae will eat as much as they need. They will not burst either. This is just a fallacy. Accounts of larvae dying from over eating are normally always to from intestinal blockage, ingestion of air bubbles or bacterial problems.
Artemia are small crustaceans that are hatched from small brown cysts. The cysts can be purchased from aquarium shops and aquaculture supply houses. The Artemia are hatched by placing the cysts into saltwater and aerating it. 18 to 24 hours later the Artemia have hatched out. The Artemia are then separated from the empty hatched cysts and are fed to the fish. Hatching is a very easy procedure however there is one serious concern with introducing empty hatched cysts along with the Artemia to the larvae. This is because the hatched out of cysts of the Artemia will often be eaten by the larvae and will cause intestinal blockage. Thedanger becomes increasingly worse with time because the larvae only start eating the empty cysts once they have become proficient at catching Artemia, which may take a few days, by which time many cysts have accumulated in the tank.. This problem can be solved however by purchasing "decapsulated cysts" or decapsulating them yourself.. The procedure is as follows:
a) place the required quantity of Brine Shrimp eggs in a glass or plastic bottle/beaker and add from 200 to 400 mL of tap water. Place this in the fridge for one hour.
b) after one hour remove the eggs and pour in sodium hypochlorite (liquid pool chlorine) at a ratio of 1:1. That is to say add at least as much chlorine as water that you have in the container. After addition of chlorine immediately start stirring the mixture. After a minute or two the eggs will start to change colour, first to a gray, then white and finally orange. When the eggs start to turn orange the decapsulation process is complete. From start to finish the whole process should take from between 3 - 5 minutes.
c) once the eggs start to turn orange they must be pored into a mesh bag of around 100 m m. They should then be rinsed in clean flowing tapwater for atleast 2 minutes or until no detectable smell of chlorine.
d) the decapsulated cysts are now ready for hatching. If a large quantity of cysts has been decapsulated at once, they can be stored for a week or two in the fridge in a strong brine solution of 300 grams per litre of salt.
Rotifers unlike Artemia cannot be purchased as tins of cysts. Rotifers must be cultured along with algae, which can be very time consuming. It is beyond the scope of this article to go into the culture of rotifers and algae as that would take up a good few pages all on its own.
To culture rotifers you will need to obtain both algae and rotifers. They can both be obtained from Florida Aquafarms. Florida Aquafarms sell a rotifer and algae starter pack which contains all the info and starter cultures to get you started.
Dry powdered foods can be added after a couple of days to help reduce the burden of continually hatching and culturing live foods. These should however only be added in small quantities as any food that is not eaten will foul the water.
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LARVAL REARING
Clownfish larvae always hatch at night, usually within three hours after dark. Sometimes however a clutch of eggs my hatch over two days on consecutive nights. After hatching clownfish have a yolk sac that provides them nourishment for atleast a further twelve hours. Since they conveniently hatch at night it means that first thing in the morning live food can be added to the rearing tank. This ensures that the larvae actually get a chance to familiarise themselves with chasing and catching the live food BEFORE all their energy reserves (inside the yolk sac) are depleted. If food was only added at the time of yolk sac depletion then many larvae would die because they have to learn to catch their own food and this takes a few hours. Infact it takes a few days before the larvae become very proficient at live food capture.
For the first two days live food densities should be kept quite high. For rotifers the density should be atleast 20/mL and for Artemia atleast 5/mL. This will ensure that the larvae will have a better chance of catching their prey. During this time the larval tank must be kept very clean with the bottom siphoned of dead larvae, detritus and feces twice a day. This is important because any decaying matter on the bottom will encourage potentially harmful bacterial growth and will lower the oxygen levels and deteriorate the water quality. Water changes will also need to be performed at a rate of atleast 25% per day and not more than 50% per day. The replacement water should be of the same temperature and pH to reduce shock.
Do not worry about siphoning out the live food when changing water. It is important to add newly cultured or hatched live food every day because the nutritional value of the live food that remains in the tank will decrease very quickly. This is because in the case of the Artemia naupilii, its mouth has yet to form and it is using up its internal reserves. The artemia also grows with time and within 36 hours may be too big for the larvae to eat. The rotifer on the other hand has a mouth but it also has little nutritional valueto it. What makes a rotifer nutritional is what is in its stomach. Rotifers also have very high feeding rate and pass out what they have eaten very quickly. The larval tank doesn’t have any algae in it there is so there is no food for the rotifer to eat. Thus after the water has been changed new rotifers and or Artemia must be added.
If the larvae have begun eating and are getting enough food they will be very active and will be seen swimming until they see a rotifer or artemia. They will then stop and watch it then snake back and lurch forward at the prey. This is natural attack behaviour. The healthy larvae will appear to have a well rounded body and should be swimming in a close horizontal position. Unhealthy larvae will tend to either buzz around on the surface at a 45 degree angle or listlessly swim at 45 degrees. The unhealthy larvae will have a hollow shape and will not be rounded.
For the first two day there will be some losses of larvae. Especially if the larvae have been transferred using the siphon method. Most deaths found on the first morning can be attributed to transportation related damage. On day two there might start to be the first of the starving related deaths. These are often the larvae which have not been able to master food capture.
From day three to eight the larvae will grow very fast. The densities of live food can be reduced as the larvae have become proficient at food capture. By now the larvae that were too small to eat Artemia first off will be able to eat them. Rotifers should be maintained at 10/mL (until Artemia are being accepted by all larvae) and Artemia at 10/mL. If the larvae have been eating Artemia they will have pink stomachs. This can be checked by scooping a larvae into a glass and shining a torch from underneath.. During this time the larval tank must be kept very clean with the bottom siphoned of dead larvae, detritus and feces twice a day. Water changes will also need to be performed at a rate of atleast 25% per day and not more than 50% per day. The replacement water should be of the same temperature and pH to reduce shock.
Day eight to eleven are very dangerous days. This is the timeframe when the larvae start to look like adults and metamorphosize. During this time the larvae are more tolerant to water conditions however they can be very sensitive to fright. It is best to not siphon the bottom or make any drastic changes to the tank at this time. Artemia can still be fed at a rate of 10/mL. A few days before metamorphosis the larvae will start to develop stripes and some of the adult colours. On the day of metamorphosis the larvae can be often found sitting motionless on the bottom.. The next day they appear to be swimming on the bottom in the clownfish fashion "waggle" and with the adult colours.
Metamorphosis onwards, the hard work is over. The clownfish can now be fed Artemia few times a day and slowly weaned onto dry foods. Its best not to move the small clownfish until they have reached atleast 14 days or until all have metamorphosized. Alternatively the fish can be left in the larval tank until they have outgrown it (only if it has a filter).
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GROWTH
From time of hatch to attaining a size of 2.5 to 3cm can take as little as 12 weeks. The rate at which the young fish grow depends on the size of the tank they are in, the stocking density, the quality and quantity of food given and the temperature. A problem to consider is that dominant clownfish will grow the fastest and will suppress the growth of the fish below. This can largely overcome however by growing the fish up all together in a large tank.
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CONCLUSION
Clownfish are a fun and educational species of fish to breed. With the knowledge you gain from breeding clownfish you can start to tackle the more difficult species of marine fish.
I hope this article has convinced atleast one person to go ahead and have a go at breeding clownfishes as you will never know how good it feels to produce a tank of 60 little clowns unless you do it!
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David Bloch
HTH
PH =)