4 in a 10 gallon minimum. So a 10 gallon with a lot of plants and no less than 4 females might work out. Some just love to fight. So within a few weeks of fighting they'll establish the leader and get along.
Who am I? Well I am a Junior Member of the International Betta Congress and a breeder of white HMPKs, red dragon HMPKs, black/red dragon HMPKs, metallic multi HMPKs, blue masked HMPKs, and now multi color HMs. Soon to add black HMs. I will be showing in New Breeder class in fall of 2012.