Instructions
Observe your fish closely before you attempt to breed them. Observing the fish ahead of time gives you a chance to determine what is normal behavior for each individual.
Watch for behaviors that appear to be out of the ordinary for the fish. Some pregnant females may become lethargic and slow moving, while they were active before the pregnancy.
Watch the sides of the fish as it swims. A live bearer like a molly will swell up and become very rounded just before she gives birth. An egg layer will have roughly the same appearance just before she lays eggs for the male to fertilize.
Look for the gravid spot just behind the side fins. The gravid spot appears larger when the pregnancy is near its end, and you may even be able to see the developing babies within that spot on light colored fish.
Watch for the fish to begin hiding more and having difficulty swimming. Both are signs that birth is close.
How to Know When Your Aquarium Fish Are About to Give Birth
Whether you are new to the aquarium hobby, or an experienced aquarist with years of experience, breeding your own baby fish can be very rewarding. Some species of fish, like guppies and mollies, are very easy to breed, while others are more difficult. But no matter what the species, it is important to recognize when your fish is about to give birth. Recognizing the signs early gives you time to move the pregnant fish to a birthing tank, where conditions are safer for the newborn fry.