How to Breed Rainbow Fish

Rainbow fish are small, freshwater fish from New Guinea. The fish are silver, but the scales reflect a variety of colors in the light. The fish grow up to four or five inches in length, if the tank is large enough. Older rainbow fish have more dramatic coloring than fry, or young fish. Different species of rainbow fish breed well with each other. The hybrid offspring reflect the colors of both parents, resulting in a dazzling assortment of new rainbows.

Things You'll Need

  • 3 aquariums
  • Male rainbow fish
  • 4 or 5 female rainbow fish
  • Aquarium net
  • Liquid fry food
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Instructions

    • 1

      Separate your male and female rainbow fish. Male rainbow fish have more vivid colors and longer anal fins than females. Look at the dorsal fins. If the front dorsal fin is long enough to trail over the second dorsal fin, the fish is a male. If the first dorsal fin is short, it is a female. Place the males in one tank and the females in another. Leave the community tank for breeding.

    • 2

      Place the breeding male in the community tank. Choose three or four females based on their color or size. Watch the male fish. It will swim rapidly back and forth, extending its fins to look as large and imposing as possible. The female follows the male and lays between five and 25 eggs near the bottom of the tank. The male swims over the eggs, fertilizing the ova.

    • 3

      Remove the male fish and place it in the tank with the other male fish. Do the same with the female fish. Adult fish often eat developing eggs or newborn fry.

    • 4

      Leave the eggs in the community tank. Depending on the species of rainbow fish, the eggs may take from seven to 14 days to hatch. The newborn fry are less than one-tenth of an inch long.

    • 5

      Feed the babies liquid fry food. When the fish are one inch long, they can be moved into a community tank, or sexed into either the male or female tank.