WEll then I'd say either a female betta or a Plakat male. And an ADF. The betta should eat betta food, the ADF bloodworms every day, and give the betta some bloodworms as a treat.
Personally I wouldn't keep anything in such a small tank, lol. That's just me though- The smallest i'm willing to go is like a 10 gallon. And I only have 3 fish in that.. lol. Buuut, I guess if you are going to put something in it, probably a Betta would be okay.. however, in my honest opinion, I don't like it. My betta loves all the room he has to swim around. But hey, ANYTHING other than those crappy little cups they keep them in is good! lol.
Cool sounds like I might get a betta and two frogs then. One thing I'm still worried about is feeding the frogs though. It's quite a long way to the nearest fish shop, and I would have to persuade my parents to take me there. It is unlikely that I would be able to get there once a month, if that. Frozen food might not be a viable option. I read somewhere about blackworms - can you culture these yourself? Is there any sort of live food that I could keep and grow myself that I could feed the frogs with?