With GREAT caution and a secondary back up plan just in case, you could try it. *It is not usually advised as Bettas are not used to having other fish around and they are very defensive about their territory. *They also do not have the defenses against some smaller fish that they do not see as threats and will allow them to nip their fins. *This can lead to a rampant case of fin rot or bacterial infection of their fins. *
Fish that are known to have had problems with bettas in the same tank are: *GOURAMIS (bettas are of the gourami family and will fight gouramis as if they were other bettas); Barbs; Sharks; Mollies; Platies; Tetras; Guppies; other Bettas ~ BOTH male and female, you cannot keep a male and a female together in the same tank except for a very short time while spawning; any fish with long fins that may be mistaken by the betta as another betta.
Bettas are grown up in small containers individually and do not know that it is allowed for other fish to inhabit their territory so they are culturally deprived when it comes to manners. *They do not usually know how to react to the other fish. *Now, I say usually because there is going to be someone come on here and say how they have a betta who lives in a community tank and does quite well. *It does really depend on the fish. *If you get a really calm betta and he is not afraid of the other fish and the other fish are really quiet and you have a really big tank with a lot of hiding places and nooks and crannies for little fish, you may be lucky enough to get away with it. *
I personally would not chance it. *But as long as you have a second tank warmed up in case of a disaster to remove the betta to, there would be no reason why you could not try. *I would not go far from the tank for a few hours after adding him to the tank though.
Rose
