The clawed frogs as two others have mentioned are 100% aquatic & stay a comfortable size for a 30+gal. Don't stick them in with anything smaller then they are though 'cause they are very predatory & have a voratious appetite. I've had two of them. They're fascinating creatures but do best in an aquarium they can dominate.
I've also had red-bellied Newts. Now these little guys had a LOT of personality. I filled the aquarium 3/4 full of water & floated cork bark on 1/2 of the water surface for them to get out of the water on. They spent 85% of their time in the water. They're also agressive & predatory but they're much slower then the frogs & can't eat anything bigger then a tetra. So they can mix a little better with fish. If I could find these again in my LFS, I'd have them in my tank in a heart beat.
I've also had red-bellied Newts. Now these little guys had a LOT of personality. I filled the aquarium 3/4 full of water & floated cork bark on 1/2 of the water surface for them to get out of the water on. They spent 85% of their time in the water. They're also agressive & predatory but they're much slower then the frogs & can't eat anything bigger then a tetra. So they can mix a little better with fish. If I could find these again in my LFS, I'd have them in my tank in a heart beat.
