They are usually africans, Mbuna to be specific ( a general term for many of the lake malawi species). Sometimes they contain peacocks, haps, and labs. Ive even seen some kribs in one once. Many times there are hybred fish in those tanks. But it is such a general term I guess they can throw anything in there so long as its a cichlid. I would avoid these, since there is posibility you will get an unpure specimin. Also, if you really want a specific type of african, you will be better off getting one that is in a species only tank, as they will be of a bettre quality.