Information About Pregnant Fish

If one of your fish begins to get fat and swollen, don't automatically assume the fish is sick. The fish could be pregnant. Before you jump to conclusions, however, you need to ascertain some basic facts. The fish has to be from a live-bearing, rather than egg-laying, family. The fish also must be a female. If your fish is indeed pregnant, some extra care on your part will help her produce the healthiest babies.

  1. Livebearers

    • Four different fish families make up livebearers. These include halfbeaks, or Hemirhamphidae; four-eyed fish, or Anablepidae; Mexican topminnows, or Goodeidae; and the largest group, the live-bearing toothcarps, or Poecilliidae. The most common live-bearing aquarium fish are from the Poecilliidae family and include the guppy, molly, swordtail and platy.

    Male vs Female

    • In order for a fish to be pregnant, it has to be female. In general, female fish are much less ornate than their male counterparts. Female guppies and swordtails have much smaller and less colorful tails than the males. Differentiate between male and female mollies and platys by checking out the front area of their anal fin, called the gonopodium. Males will have larger and longer gonopodium than the females.

    Signs

    • One of the most obvious signs of a pregnant fish is the size of its belly. Female fish that are expecting get very fat and bulging in the abdominal area. Some fish get so wide they will often look like little boxes swimming around. The fish's belly will continue to swell and darken as the due date draws nearer. There is no exact way to determine the due date, but most fish give live birth about one month after becoming pregnant.

    Care

    • Pregnant fish need a little extra care to stay as healthy as possible. Include live food in her diet, in addition to quality flake food. The live food helps the young fish start out larger and more robust than they would on a flake-only diet, according to Aquatic Community. Also pay extra attention to the water quality. Immediately scoop out any detritus and uneaten food. Aquatic Community recommends changing 25 percent of the water at least once a week to keep the pregnant fish in optimum conditions.

    Birth

    • Once your fish gives birth, the baby fish are going to need plenty of protection. Both male and female fish may eat their own young, so give the babies plenty of foliage and areas in which to hide. A breeding trap, which is a plastic container that separates the babies from the rest of the tank, is one option. Another option is to move the pregnant mother into a separate tank when she is ready to give birth. Once the babies emerge, leave them in the separate tank by themselves and put the mom back in the community tank.