I would build it out of plywood and then cover it with the pond liner, if you buy it big enough you might be able to put 2 layers.. my only consern would be when they start to breed... they like to dig, and might bit down on the pool liner and bite a hole right into it.. but oher than that.. I had 21 piranhas at 1 time they would breed and seem to hate each other, but hung out like they were cool.. but they would nip plants and stuff, I think some of the nipping was down when they got startled.. but I don't think you'll have a problem
I think the problem you might have though is heating it.. or maybe them jumping out.. but i don't really think there jumpers...
I think the problem you might have though is heating it.. or maybe them jumping out.. but i don't really think there jumpers...
