I am planning on making a tropical stream-side themed water fall paludarium with a spray foam background. I want it to have most of the bottom to be aquatic (2-3 inches of water) with large river rocks sticking out. The background, I am thinking will be steep, but still easily climbed, with large rocks jutting out as places to hide/ bask/ hang out. It is at 50 gallon tall hexagonal tank, and I want some kind of small - medium sized semi-aquatic salamander or lizard. Additionally, I think it would be nice to have some sort of smaller, mostly aquatic animal that doesn't bother the main attraction, and isn't bothered by it. For this, I am thinking some sort of small crab or shrimp, as long as the (hypothetical) newt's poison doesn't harm it. Does anyone have a suggestion for what pairing would or wouldn't do well in this sort of conditions? Any feedback is appreciated.