they're really more detrivores than anything... if you keep them fed with a decent food, supplement w/ iodide (for shell molting/shell formation) they'll leave the plants alone..
i've been thinking about some kind of "flow through" structure for them.. something liked stacked pallets with a bunch of pvc cutoffs between the layers
if i clear up some floor space in my basment, i'm going to try redclaws.. i'll use a water bed heating pad(s) to keep the temps of their water up, with the pool on couple of inches of isulation.. bubbble wrap the pool, and some floating plant rafts for the surface