How to start breeding tropical marine fish
If you have been successfully keeping saltwater fish in a marine tank for a while then perhaps you would like to move on to breeding your fish.
Many keepers of saltwater aquariums are content to just keep fish. For the brave few I will outline the basic steps that you need to be take in order to ensure a healthy brood. I will assume that you are familiar with the basics of marine aquarium care.
Equipment and food for breeding marine fish
Besides having a male and female fish, you will need to do some preparation for your fish if you would like to enjoy successful breeding:
• Breeding tank—You will want to setup a separate bare-bottom breeding tank that your fish larvae can comfortably live in until they become adults. It may help to have several tanks ready, depending on the size of the brood you plan on keeping. Large filtration is out of the question, but a simple air stone can help keep the water moving.
• Live food cultures—Fish fry will thrive if they given a continuous supply of live food. You will want to begin preparing your live food cultures before breeding starts so that you do not have to rush after your fish have bred. It is recommended to culture both rotifers and baby brine shrimp as the best two starter foods.
Many saltwater fish will begin their lives in a larval state, which often requires the set up of complex larval rearing systems in which multiple breeding tanks are connected to the main tank through a sump and constantly fed rotifers and live food cultures. If you are breeding your first tropical marine fish, it is advisable to choose fish that you can raise in a simple breeding tank without having to worry about the larval phase.
Selecting which marine fish to begin breeding
Since some marine fish require such a complex breeding set up, you, as a beginner, should focus on breeding easier species of saltwater fish that are simpler to breed. Avoid breeding fish that have a “pelagic larval phase”. The following list of fish have fry without a protracted larval phase.
• Banggai cardinals,
• Bristletail filefish,
• Green wolf eels,
• Neon gobies,
• Dottyback fish.
If you have a healthy pair of any of the above species in your tank, you can reasonably expect them to breed at some point. Most saltwater species will breed on their own when kept in excellent water conditions. However, certain species may take a long time to form a sexual pair.
If your fish are just not breeding despite keeping excellent water conditions with lots of hiding places then try moving your pair of fish into a low-light spawning tank. Orchid dottybacks, for instance, will breed readily when paired off in a small, covered tank with some decoration.
What to do when spawning begins
Generally, your job will begin when the eggs hatch. Up until then, one of the parent fish will usually defend their eggs, and will generally do a good job of it. Once the eggs hatch into larvae, however, you need to get them into a separate tank and get them fed.
Collecting your larvae from the main tank can seem like a difficult task, but one important tip can help: fish larvae tend to be attracted to light. To collect your larvae, follow these steps:
• Turn off the lights and water flow in your tank,
• Shine a small flashlight at the corner closest to the larvae,
• Let them accumulate in the light for a minute or two,
• Use a dip cup or siphon to collect them and deposit them in their own tank.
Raising the larvae of marine fish
Feeding the fry is the main stumbling block in reproducing marine fish. Many aquarists fail at this stage or lose all but a few of the fry. There is definitely money to be made for the aquarist who can successfully feed and raise a whole brood to a saleable size regularly.
Your fish larvae will need to be fed frequently and in large quantities. In the sea they would be surrounded by a rich variety of live plankton. Larval fish are voracious eaters and their appetite will surprise you. Moreover, their waste and waste of their live food will make frequent water changes necessary.
It is important to remember that your marine fish fry, being so small, will be unable to catch all of the food in the tank, and you will inevitably lose some food to waste and even some fish to starvation. These larvae need to have food within several millimetres of themselves in order to catch anything, which means saturating your tank with rotifers or plankton. Moreover these rotifers must be fed too. The rotifers must be fed with nutritious live algae. Ultimately this nutrition passes to the larvae via the rotifers. Algae can be raised with a light source and nutrient rich saltwater.
In fact, you may find that you are quickly running out of food to feed your fish, which leads to a very important rule: Never raise more fish than you can feed. You may have to cull some of the less fit members of the brood in order to realise this goal, but it will save the rest of them and ensure the health of the rest. A healthy minimum concentration would be 10-15 rotifers per millilitre of aquarium water in order to simulate the plankton they would find in the wild. A good system is to have and feed the rotifers in the same tank as the larvae. This, though, puts a heavier burden on the raising tanks oxygen demands and ammonia levels.
With frequent water changes, a well-oxygenated tank and lots of food, you should start seeing growth in your fish. The water changes will be very important since both your fish and your rotifers will cause ammonia levels to climb, and your filtration will be limited to fluidised sand filters, trickle filters and protein skimming – anything that uses greater flow will suck up the larvae.
Caring for your fish larvae
When breeding tropical marine fish, you will need to take care against bacterial infection. Siphoning out the waste properly twice a day should help reduce the risk of harmful bacterial colonies developing on decomposing organic waste. Your fish larvae have brand new immune systems that will not protect them from infection.
Protein skimming, again, can help greatly here by removing organic material and bacteria from the water column. A UV steriliser is also a very good idea for your breeding tank. If any of your larvae get sick, they need to be culled immediately to protect the rest of the brood.
Once your fish are large enough, you can begin feeding them baby brine shrimp as they gradually mature into juvenile fish and become ready to be weaned onto a diet of dried foods. While rotifers are ideal for the very beginning, eventually your fish will grow too large to be effectively fed by these tiny organisms.
One last important thing to consider: Since your larvae respond to light by moving towards it, any light source outside the glass of your aquarium will attract them. The result of this is that it will cause your larvae to bump their heads against the aquarium glass until they die. This behaviour also occurs if the larvae have run out of food. To prevent this you will need to cover your aquarium’s bottom and sides with a dark material.
If you have followed these instructions and researched the needs of your individual species, you will be well on your way to successfully breeding tropical marine fish for the first time!