Spawning season spans between May and August in their natural environment. In a controlled environment with proper ideal "natural environment like" conditions such as, spawning temperature water around 67 to 80°F, light fluctuations, area to build a spawning nest, and well-planted aquariums can reproduce all year. A female bluegill can lay between 10,000 and 60,000 eggs.
Males create a spawning bed in shallow water, and If a female chooses this mate, she will start to swim with the male. Together they will settle in the middle of the nest, touch bellies and spawn. After the female drops the eggs, the male chases her out of the nest and guards the eggs. The male watches the eggs until they hatch which usually occurs 5-7 days later, and the new fish swim off on their own. During this time he can be seen cleaning the nest and aerating the eggs with his pectoral fins. Once hatched the larva swim up out of the nest and filter feed on zooplankton until they get large enough to eat small insects. At this point, bluegills can get cannibalistic. Bluegills are excellent predators, the parents will begin to eat their young, so you will want to gently move the larva to a smaller tank.
*Catfish coexist well with Blue Gill because they are bottom feeders whereas Blue Gill are top feeders, and they have similar water requirements.*