Join Date: Mar 2011
Location: Albuquerque, NM
You can't have any other fish in a 2.5 gallon tank. The betta will probably kill them eventually, not to mention the filthiness that will quickly build up in such a small tank.
If you want to have tank mates with your betta, I'd suggest getting and cycling a 10 gallon tank. There are several threads about tank cycling. And if you are getting a 10 gallon, you can cycle it with a betta (with the proper maintenance), but it would be unwise to cycle it with more than just 1 betta.