Items you will need
Air pump and airstone
Clay pots or rocks
Fathead minnows (Pimephales promelas) are small, silver fish that are used often as bait for other fish. The males will grow a wen on their head, which is extra fatty tissue that makes them appear larger than they are to intimidate predators. The females do not grow a wen on their head and are often more plump. Fathead minnows are easily bred in aquariums. The female can lay up to 700 eggs and they hatch within four to eight days. The male fathead minnow will protect the eggs until the fry are born, and then leave to reproduce.
Get several 10 gallon aquarium tanks. Set them up for the right temperature of water for the fathead minnows, between 72 and 74 degrees F. Place a light to stay on for at least 15 hours a day. Use an air pump and airstone to increase oxygen in the tank and to help with water flow within the tank.
Place an object that the minnows can lay eggs in. You can use clay pots and place them on their sides and fill them halfway with pebbles. Or, you can use rocks that have overhangs. Use something that you can easily remove from the aquarium with the eggs inside.
Place two male and four female minnows in the tank. This will allow the male minnows have several females to reproduce with.
Plan to remove the eggs. Have a second tank available to move the unhatched eggs to. If you do not remove them before they hatch, it will be difficult to remove the fry. The adult fish also tend to eat the fry.
Keep the overhhanging rock or clay pot with the eggs you are removing. Place the pot with the eggs into another tank. Replace the rock or clay pot into the tank with the adult minnows, so they can lay eggs again.
Feed the fry four days after they hatch with ground-up flake fish food. You should feed the fry three or four times a day, and change 50 percent of the water in the tank at least once a week. Siphon out uneaten food when you change the water.
Avoid placing too many fathead minnows in one tank, since there will be an over abundance of breeding and it will be harder for you to keep up with. Place one batch of eggs in one tank at a time.