Amphibian Tank Question?

i have a tank that is 24"x15"x12" with a 'clip on the side' filter. If i put aquarium sand on the bottom and added some decor and a hide what would i be able to keep in there. thanks. i already have 2 chinese fire belly newts and an african dwarf frog so i was thinking some sort of frog/toad or maybe even a salamander or an axolotl. i'm not fussy so what do you think?