Choice of fish is a personal decision as well as a habitat and compatibility decision. Remember "Agressive" is a relative term with fish. Some fish hate only the same kind. Others hate different fish. Some hate everybody. Knowledge of the species is crucial in selection. Fish referred to as non-agressive can still be agressive toward some fish, other males, other females, or even only in mating season or while hungry. Consult a knowledgeable store owner for more information.