When you say pvc tube rings i assume you mean the nutrient film technique (nft) which is used in hydroponics? If so square plastic fence posts work better according to one text I have. Or perhaps i hsve it all wrong as i'm most familiar with raft culture.
One down side to nft is your water has to be really clean of particulates or they clog. Was also told by Myles Harsten at our recent fall aquaculture conference to stay away from the verticle columns as they get clogged with roots.
Last edited by Cecil Baird1; 10/19/13 12:52 PM.
