I was thinking about UGF and came up with the following: What about putting a spaced coil of hard PVC tubing(say 1/8 inch diam) under the substrate and pumping warm( or hot) water through it in a closed loop system? Any thoughts on this?? -- _____________________________________________________ "A Bad Day Fishing Is Better Than A Good Day At Work" 1°: Macaw at tiac_net 2°: robert_s_woolley at ffn_mhv.net Web Page: http://www.tiac.net/users/macaw