If you suspect your parrot fish is pregnant, it is important that you keep her isolated from any other fish to ensure her safety. Do so when her belly starts to look boxy from behind. After she has her eggs, you will want to continue to keep her and the eggs away from others until 10 or 15 days after they hatch.
Parrot fish are able to change genders, colors and patterns. So while the sex of a parrot fish might be hard to determine, it is usually easier to tell if your parrot fish is pregnant. Some simple observation of visible cues will help you decide.
Observe your parrot fish. Pay attention to where in the tank she spends most of her time. If a parrot fish is expecting, she typically will stay in one area the majority of the time.
Examine your parrot fish's body. Pregnant parrot fish will gain a significant amount of weight in a short period of time.
Look at the sides of your parrot fish. Most pregnant parrot fish will show a visible bulge on both sides.