Most thumbnails are out of the question unless you look to get fantasticus which are more terrestrial. Auratus are beautiful but with that beauty comes a shyness. I would recommend terribilis as well. Great communal frog, hearty feeders, and bold as the sun is bright. Tincs are great frogs but not great in groups. If you like smaller frogs, E Anthonyi santa isabel are great communal frogs and you could keep anywhere from8-12 In a tank that size. They have a lovely call, good feeders, and are pretty bold as they mature.