If you have a tank with livebearing fish, such as guppies, platies, swordtails, or mollies, chances are you will see baby fish at some point. Livebearing fish breed very easily, and the females incubate their eggs inside their bodies. When the eggs hatch, they emerge from the female, giving the appearance of being “born.” Baby fish are extremely fragile, and care needs to be taken with them, or the other fish in the tank will eat them.
Baby fish are called fry, and they can often be spotted in the rocks and plants of an aquarium. Fry resemble tiny fish, and fry of small species, such as guppies, might even look like little insects in the tank. If you find baby fish, there are some steps you should take to ensure that they are not eaten by their tankmates.
If you are going to have livebearing fish in your tank, purchase a breeding trap or net even before you notice baby fish. This way you will have a place for them when they do come. A “pregnant,” or gravid, fish can be spotted because she will have a dark spot near her anal fin, and the spot will grow larger and larger. This spot is the eggs. If you want to remove the female from the tank while she is gravid, you can place her in a breeding trap until she has her babies. She will probably eat a few of them, but they will have a much greater chance at survival if they are born away from the other fish. There are special breeding traps on the market that allow the fry to fall into a portion of the tank where the mother cannot reach them. This is great, as long as the fry have the ability to reach the surface of the water in their portion of the tank. One of the first things fry must do after hatching is swallow some air to fill their swim bladders. If they do not have access to the surface, they cannot do this.
If you notice baby fish in the tank after they have been born, remove them and put them in the breeding net. Take care when netting baby fish, as they are extremely fragile and will bury themselves into the aquarium gravel, often injuring themselves in the process. Try to sneak up on the fry with the net. If you see one baby fish, watch your tank closely, because there is a high likelihood that there are more hiding in the tank somewhere. Broods are usually between 15 and 50 fish, so keep your eyes peeled.
Once your fry are safely isolated, you need to feed them. Fry can choke easily on food, so do not feed them traditional flake food. Your local pet shop will sell a powdered “fry food” that is small enough for them. Live food is excellent for fry once they are a few weeks old. Freshly hatched brine shrimp are one of the healthiest food choices for fry. You can purchase brine shrimp hatcheries at your local pet store. They are very easy to grow.
Keep in mind that you will have many more fry than you can possibly keep in one aquarium. Think about others you could give some fry to, or contact a pet store to see if they would like to sell some. Isolate them, then feed them a healthy diet. Once they are large enough that they will not become food for the other fish, you can release them back into your tank.