Heavy Metal Guppies

[xoxoxoBruce]

OK, Wiki names these as common aquarium fish.

Cichlid keeping aquarists tend to divide cichlids into groups based on regions such as Central America, South America, Madagascar and India, Lake Tanganyika, Lake Malawi and Lake Victoria. Others divide the cichlids using the combination of geographical, taxonomical, and behavioral criteria. Some notable groups resulting from this type of categorizing are the mbunas, haplochromines, dwarf cichlids, and shell dwellers.

Cichlids from Lake Tanganyika were first collected by German hobbyists during the 1930's. However, it was during the 1970s and 80s that the cichlids from lakes Tanganyika and Malawi began to become popular aquarium fishes. This trend continues to the present unabated.

Perhaps the most commonly encountered species in retail aquariums is Pterophyllum scalare from the Amazon River basin in tropical South America, known in the trade as the "angelfish". Other cichlids commonly stocked by retail aquaria include:

Astronotus ocellatus (oscars)
Cleithracara maronii (keyhole cichlids)
Hemichromis sp. (jewel cichlids)
Labidochromis caeruleus (electric yellows)
Mikrogeophagus ramirezi (blue rams)
Pelvicachromis pulcher (kribensis)
Sciaenochromis fryeri (electric blues)
Symphysodon discus (discus)
Species of cichlid can be kept in aquariums with other fish, however, many cichlids are aggressively territorial or predatory towards smaller fish. Conversely, some cichlids, such as Apistogramma or Julidochromis spp., can be timid in the aquarium. In such cases the use of dither fish is recommended.

So I guess that would be the maximum of your choices, and probably less. Fish on.