Iāve been planning a 40 Gallon breeder, and Iām trying to find a good centerpiece fish. It canāt get bigger than 8 inches long. It also canāt be anything above semi-aggressive. And it canāt be something that will eat small fish, because I may keep blue tetras with it. It also canāt be super tall, because 40 gallon breeder tanks are only 16 inches tall.