Certainly bigger is better here. These fish are reportedly some of the meanest out there! I had read that they are best by themselves, but a breeding pair is a must if you want more than one. Two seems to be the limit in any size tank because of their aggression, but then again, I have only read about them and never kept them so I dont know how accurate that is. I have read in many places though that if you can get them to breed, most of the fry will not make it very long and what does survive is going to be about 90% colorless because of something to do with their overly hybrid geneology.
I guess they are very good 'feung shue' though!
If you do get some, I would love to hear about your experiences though and pics would make it all the better!