Why does your Siamese fighter male swim rubbing itself?

His skin is possibly being irritated by the water. Are you looking after the fishes water properly?. The basic rules for keeping fish successfully are. :- 1 inch of fish needs at least 1 gallon of water (a Betta is a 3 inch fish). Every tank must have a permanently running 'cycled' filter. Every tank must have at least 50% of its water replaced every week. Bettas are tropical in their requirements and should be kept at around 78F.