How to Raise Baby Fish Successfully
Dr. Roy Yanong
Birds do it. Bees do it. And, yes, fish do it too. Fish need to be compatible, so make sure your breeders are the right age and size.
But when fish are in an aquarium, it's up to their owner to make sure they're in the mood – and to make sure their progeny, or fry, are healthy.
As with other animals, good health begins with healthy parents and continues with proper environment, feeding and a good understanding of the needs of a particular species.
The Right Environment for Breeding
Size matters, especially when it comes to tanks. So make sure yours is roomy enough for courting and that the water is fresh and clean.
Stock your tank with the correct ratio of male to female fish. For some varieties, a little competition can be a turn-on – or a turn-off.
Make sure your fish are well fed.
Bringing Up Baby
When everything's done just right, the fry (newly hatched fish) will follow. Keeping them alive is another story.
Fish fry are often food for other fish. And some fish eat their own young. To keep the little ones safe, relocate the adults to another tank after they've laid their eggs or released their fry.
There are, however, some notable exceptions. For example, the anabantoids or labyrinth fish – whose members include the gouramis, fighting fish and paradise fish – protect their eggs in floating bubble nests built by the males. The males guard these eggs against all would-be intruders, including the mothers. Once the eggs have hatched, the male's job is done and he's off to spawn again.
Creating a Good Home
Because of their immaturity and size, fry placed in tanks with poorly filtered water or poor lighting are less likely to survive. Their immature immune systems make them very susceptible to bacterial, fungal, parasitic and viral diseases. Here's what you should do:
Check the water quality. Water should be changed frequently, and ammonia and nitrite levels should be zero. Some fish prefer hard water, some soft – check the needs of your fish before setting up your tank. Many fish breeders use sponge filters - which remove ammonia and nitrite – in their fry tanks. Tiny organisms, known as zooplankton, often grow in and around the sponge, providing the fry with live food.
Check aeration. Too much of a good thing can harm the fry. In a small tank, churning water can be dangerous to fragile fry.
Check the thermometer. A range of 76 to 80 degrees Fahrenheit is good for most common tropical freshwater fish, although koi and goldfish prefer it cooler.
Watch calcium levels. Many fish obtain their calcium directly from the water. Keep levels at or close to 20 parts per million.
Many fish hatch as larvae with an attached yolk sac, which provides nutrition until the larvae are capable of feeding on their own. After that, baby fish must eat at least four to six times a day because they have very high metabolism and lack fully developed digestive systems.
Fry like their food live. Brine shrimp nauplii used to be one of the most common fry feeds, but it is increasingly expensive. Other small live foods include daphnia and microworms, available from some aquaculture-supply companies as well as through hobbyists advertising in trade magazines.
Infusorian, which is essentially a plankton cocktail, is another common first food. These cultures are often found growing in and around aged sponge filters.
Commercially prepared fry foods can be used for some species.
After the first few weeks, most fry can be weaned off live foods and on to dry, prepared diets. Once this happens, the hard part's over. But some fish, like cichlids, get more aggressive as they get larger and if they don't get more space – other fish could become lunch.