Instructions
Check that the Betta fish is female. Betta females are smaller, and have much smaller fins than their male companions. If the fish has long, colorful fins it is likely a male and will not lay eggs.
Examine the Betta fish for white vertical strips along her body. According to the Beta Fish website, these white stripes indicate the female is fertile and has produced a set of eggs. Since Betta fish do not reproduce by live birth, this is as close as a Betta Fish comes to being pregnant.
Look for a small white dot on the underside of the fish. This is the ovipositor, which is a tube the eggs are released through. A visible or extended ovipositor indicates the presence of eggs in the fish's abdomen.
Watch for the male Betta fish to build a bubble nest. The male won't begin to do this unusual activity unless there is an egg laden female present in the tank.
Look for a plump or swollen abdomen on the female Betta fish. The website AskTheVet.com explains this is a sign the fish is full of eggs.
How to Tell If a Beta Fish Is Pregnant
The Betta fish, also known as the Betta splendens or Siamese fighting fish, is a common and colorful freshwater aquarium resident. Betta fish live in shallow, low quality water in their native Laos and Cambodia say the experts at New Aquarium Information. This makes them easy to keep, even in a small tank with poor water quality. Breeding betta fish requires a female fish, which can be difficult to find. Another challenge is telling when a female betta fish is fertile and full of eggs.