I have a 6x2x2 with a nice group of fish in most are small fish around 5inch along with a group of of 13 silver dollars, one of my fish is a male jd who is around the 10 inch size, he has a female around 7inch for company but he spends most of his time facing the back corner of the glass and not much time anywhere else in the tank, there isnt anything in there of any size to bully him so im guessing he iz maybe unhappy, any ideas why?