I wouldn't recommend a betta with your fish.
Either the Barbs or the Tetras can be nippy and too active for a slow moving betta or the betta can be aggressive with them.
Stress can also play a factor. Even if no one gets hurt or killed, they can become ill.
Bettas in community tanks aren't really recommended. Most do better as a solitary fish.
If you want a betta, a 5g tank would be perfect.
Jaysee, thanks, I missed the Gourami. Gouramis and bettas aren't compatible.
I started off with cherry barbs in a 20 gallon and they were just not happy. They fought amongst themselves constantly. Once I moved them to a 30 gallon, that seemed to give them the elbow room they needed and they became very peaceful.
Jaysee: I have some questions about adding shrimp. Would the fish attack them, What type/types could/should I get, how many should I get, how do I clean the tank without sucking them up, can they be with the BN Pleco, and do they have any special requirements or requirements different from the fish I have on the stocking list a few posts ago?
LyndaB: I could get 7 of them if that would help, but I feel like that's too many. Are there any other barbs that could do well in the tank?