I don't know much about frogs (though I doubt, from the little I do know, that even a small frog would be happy in there). I have several enclosures of that size where I keep Sphaerodactylus macrolepis, tiny geckos that are about 1 1/2" as adults. You can find out more about these and other tiny geckos here: dwarfgeckos.com
Aliza