You can, but the only frog I know you could get that would co-exist with most fish are African Dwarf Frogs.
African Dwarf Frogs grow to a maximum of only two inches, are very peaceful, and entirely aquatic, not requiring a raised platform above water. They should be kept as a duo or a threesome and they need hiding places, preferably things that resemble thick plants or shrubs. There is one problem though: They are slow feeders and often the other fish will eat their food before they can get to it, so be prepared to deal with that.
