If you plan to breed your aquarium fish
, you will need to know how to raise the fry after they have hatched. While some species of fish care for their young for a few days or weeks after birth, many do not show any parental behaviors – in fact, many species will eat their own young. To protect your developing fry it is important that you provide them with a safe environment in which to mature. In addition to providing them with a place to grow, you will also need to offer your fry food that they are capable of eating. Depending what species you are breeding, the fry are likely to be very small and will not be able to accept traditional flake foods or pellets. Newly hatched fry will require tiny, preferably live, foods in order to grow quickly during their first few days of life. One of the best foods for newly hatched fry is infusoria.
What are Infusoria?
In the aquarium trade, the word “infusoria” is used to describe all kinds of microscopic aquatic organisms, both plant and animal. Infusoria are much smaller than brine shrimp nauplii so they are the perfect food for fry that have just hatched and have absorbed their yolk sac. The first few days of life are incredibly important for newly hatched fry – if the fry do not receive adequate nutrition during the early stages of their life they may fail to develop properly and could even starve to death before they grow large enough to accept brine shrimp nauplii and other foods. Infusoria were first discovered in 1763 and, since then, over 2,000 different species have been discovered. The particular type of infusoria used to feed newly hatched fry is not important – all types of infusoria are ideal to provide fry with live food
small enough for them to eat after just hatching.
Tips for Culturing at Home
Especially if you plan to breed your fish regularly, it is a good idea to learn how to culture infusoria at home. By learning how to culture your own infusoria, you can ensure that you will always have a supply of fry food on hand and you will save a great deal of money not having to purchase it multiple times. The easiest way to culture infusoria is by collecting water and/or filter debris from an established tank. Start by cleaning out a glass or plastic jar to culture your infusoria in. Next, fill the jar with water from an established aquarium – water from planted tanks
After you’ve filled the jar, add some type of vegetable matter such as a few leaves of lettuce, potatoes, rice or debris from an active filter. After you’ve prepared the culture all you have to do is wait – some hobbyists recommend leaving the jar out in the sunlight to increase infusoria production but you can decide for yourself. After a few days you should see the water begin to turn cloudy or green. When this happens, it is a sign that the infusoria have reproduced sufficiently to be harvested.
Using Infusoria as Food for Fish
When using infusoria as food for fry you need to keep in mind that infusoria are microscopic so even a small amount of water from the culture jar will contain many infusoria. For this reason, it is important that you do not add too much water from the jar to your fry tank at one time because the uneaten infusoria will die and could pollute your tank. The easiest way to harvest infusoria is to use an eye dropper or turkey baster to collect a small amount of water from the top of the culture jar and to squirt it directly into the fry tank. You should plan to feed your fry small amounts of water from the infusoria culture at least twice a day so they will grow quickly.
After a few days, you may notice that your infusoria culture jar begins to develop an unpleasant odor – this is likely due to the decomposition of whatever vegetable matter you used to start the culture. When collecting infusoria to feed your fish it is important that you do not collect any of the vegetable matter. As the vegetable matter decomposes, this will be more difficult to accomplish so it is a good idea to start a new culture every 3 to 4 days so you always have a fresh one to work with. Depending on the species of fish you are breeding, most fry are ready to accept slightly larger foods like brine shrimp nauplii
after a week or so of feeding on infusoria. Start by offering a mixture of the two – when you see that the bellies of your fry are pink or yellow (the result of feeding on brine shrimp) it is safe to discontinue the use of infusoria.
Bonus: Constructing a Fry Rearing Tank
As was mentioned in the introduction to this article, your best bet in raising a majority of your eggs to maturity is to separate them from the adult fish immediately after spawning. Most species of aquarium fish do not care for their young after they have spawned the eggs, so it is best to raise them independently. To create a rearing tank for your fry, choose something large enough to accommodate all of them without being too large that the fry are overwhelmed – a 10-gallon tank is usually a good place to start. Set up the tank to mimic the conditions in your breeding tank (or in your main tank if you are using that to breed your fish).
Once your fish have spawned, carefully collect the eggs and transfer them to your rearing tank. It is a good idea to leave the bottom of the tank bare to facilitate easy cleaning, though you may want to provide some mossy plants to give your fry places to hide. Equip your rearing tank with a sponge filter to provide mechanical and biological filtration. It is not recommended that you use a more powerful filter in a rearing tank because your fry could get sucked up into the filter. Sponge filters are inexpensive, easy to maintain, and provide for the basic filtration needs for a rearing tank. As you feed your fry the infusoria you have cultured, you will need to perform regular water changes to keep the tank water clean. If you feed your fry often enough, they should grow very quickly during the first few weeks and will be ready to be separated into larger grow-out tanks once they reach 1 inch long.
Breeding aquarium fish can be an exciting and rewarding experience but it can also be quite a challenge. If you hope to succeed in breeding your fish you will need to know how to feed your fry to ensure that they survive. Infusoria are a great food for fry and they are easy to culture at home.