Well there are a number of freshwater puffer species. Probobly the most common is the Dwarf Indian Puffer. However, they are all semi-aggressive fish and will not do well with your fish.....the cories in particular. I do have a pair in my community tank with no probelms, but you have to be very careful with what community fish you put with them. In my experience, cories will definatley get beaten up pretty bad, but fast moving fish small tetras do fine as well as other semi-aggressives. Generally they are not reccomended for community tanks though.