put the pothos in the water along shoreline. the roots will grow in the rock. the gravel is fine as long as it can't be swallowed. I never liked the dried moss though. too many problems with that stuff. creeping fig is good for another plants. short snake plants are good too. do you have corkbark/driftwood/ shale,sandstone rock pile for frog to hide under/in. that temp range is a little low but ok. most amphibs like 80 day/70 night but firebellies are good a little lower.