Floating frogs (occidozyga lima - dunno if that's spelled right.). Provide floating plants and leave 2 inches or so without water at the top of the tank. A 55 gallon is probably too big for ADFs - it is too deep and the frogs actually like small water areas (in the wild they are often found quite happily living in puddles). In a 55 firebelly newts should do fine with fish if there are loads of floating plants and some floating cork bark for them to climb out onto. Again the water level will need to be reduced. Depending on the size and speed of your fish you could get a Spanish ribbed newt - again this needs cork islands, and can get up to 12 inches. If you want a slightly differernt community fish, how about a medium sized synodontis species? Marbled synos are peaceful, but not very active though. Synodontis nigrita and synadontis eupterus are active during the day, but I don't know how big they get. as far as I know they shouldn't bother community fish.