All corys will shoal together whatever species. Some have a distinct need for their own species and will spend most if not even all of their time together as a species. Other species seem to be happy just so long as other corys are near them. For 15 years I have maintained large groups of several cory species and several have spawned. In fact, I presently have a couple of Corydoras duplicareus
fry growing up with the others in the 115g. One of these i rescued from the canister filter when I cleaned it about 6 weeks ago; spotted something swimming when I had taken out the baskets, and netted it out and into the 10g where I thought it would be less likely to get eaten, since it was only 3/8 of an inch. Two weeks ago it had grown to 5/8 so I put it in the big tank. I spotted one or maybe two others recently.
There are now 3 species, perhaps more, with albino variants made by man. Corydoras aeneus
and Corydoras paleatus
are the two more common ones, and there is an albino C. sterbai. Not sure how many others. Each of these will obviously relate to that particular species.
NickLing, on the emerald, that is likely Brochis splendens
, related to the corys, though it might be Corydoras aeneus
. Click the shaded name to see the profile info and photos, it will explain how to tell them apart. And it needs
others, at least 3. These fish are highly social, living in groups of hundreds in their habitat, and without others around them they will be stressed. You can read what this does here: Stress and Freshwater Aquarium Fish