African Dwarf Frog in Small Tank?

If the tank is filtered, if the tank is cycled, if you have a cave and plants so the frog can hide, if you can feed frozen bloodworms (not freeze-dried), if you can do 30% water changes twice a week and if you have a backup plan, then, yes, you could have an ADF.

Make sure the lid is a tight one as ADF can escape and die rather quickly. I wouldn't put two ADFs and a Betta in a 2.5. Can you get at least a five gallon and keep the 2.5 as a backup if it doesn't work out? Then you could have two or three and they do like to be in numbers as they're very social critters.

Thanks for the advice! I can't get a 5 gallon tank right now as I've spent well over $100 this week on this fish trying to make him happier and buying him random stuff he doesn't need haha.
So I'll probably wait a month or so to get him a bigger tank then if that works out I might add the companions.
Thanks again for your help!

You are quite welcome. I always tell people to get the biggest tank they can afford. There are some really nice 10 gallon setups for under $50 if one has space. And the nice thing is a 10 can be divided so one can have a second or third Betta. ;-)

And I forgot the most important part:

Welcome to the forum!!!