By "dwarf" anglerfish im guessing you mean A. pictus. Frogfish are notoriously difficult to take care of and if you haven't done much reading on them I don't suggest you buy it. A. pictus (considering it is A. pictus, they are impossible to ID without a photo) only gets about 4 inchs long and they dont do much besides sitting around all day so i 10-20 gallont ank would be ideal. If the fish eats frozen (which means you're lucky) you will want to feed it frozen silversides, they are small eel looking fish that you can get at the LFS. If they dont you will have to feed them glass shrimp and live fish. I would reccomend feeding it once every two to three days and do not overfeed as they will eat until they die.
IMO you should do ALOT of reading about anglers before getting one. They can be tricky.