I have 3 pictus cats and from what I have seen they enjoy each other's company. I think 2 in a 30 would be fine. Provide a couple of caves but leave the bottom fairly open. Maybe a couple of plants for them to chase each other around and you should be fine. I kept my 3 in my 35G for a couple fo months and they never seemed to have an issue, their behavior is exacly the same in the 75G now. I also think you could get some upper level fish to even the tank out since these guys are total bottom dwellers. Watch how you feed them too, mine will eat anything and not stop eating. I actually had one eat all 4 peas I put in the tank for all the fish to eat, I could see the outline of each pea in his stomach!