11-01-2010, 03:28 PM
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Gina, the fish on the right I would suggest is Corydoras elegans. Many species of cory, including this one, have considerable variation from fish to fish or locale to locale. The left fish may be the same species.
This species is very similar to C. nanus, and slightly less so to C. napoensis, but C. elegans is much more common in the hobby so I think that is what you probably have.
The "friendly" behaviour is common among corys of all species, male or female. They are a highly social fish, which is why they must be kept in groups. In the wild they occur in groups of hundreds of the same species, and sometimes 2 or 3 species but still hundreds of each. In sufficient tank space, five of any one species is ideal, but 3 of a species will work in smaller tanks or if you have more than one species. They sometimes interact with other species, sometimes only their own; but more than 2 corys is needed.