I'll be getting a gold nugget pleco in the next week or so for my 50g and I was looking at making caves for it to hide in. It's 2.5 inches from what the store told me and I was wondering if 1.5 x 6 inch PVC pipe would be large enough for it. Would they require caps on one end to make it more cave-like or would I be looking at a stagnant water problem?