For the most part, this has been happening since I stocked my 29 gallon with 2 Dwarf Gourmis, 16 tetras, 3 Mollies, and 6 coryfish. All of the fish, except the coryfish, have been "attacking" the other fish (I believe fin-nipping is the more appropritate term). What is interesting is that only gourmis will only attack gourmis, mollies only mollies, and tetras only tetras. It's quite consistent. What could be the problem?