Insulation is the key with these, but one should be plenty! Head off to Home Depot, or Blowes, and pick up a small roll of insulation, and a roll of reflectix (The chrome looking bubble wrap.) Get a roll of METAL duct tape. That stuff sticks to everything, for better or worse. Wrap with insulation, then a layer of reflectix. Secure with tape. Make a removable piece of double layer reflectix for the lid (Or much better, 1" foam board) with cutouts for your netpot (s). Get a cheapo digital thermometer for the water ($12 at Petco). No light leaks. Period. You should be more than set then. I kept my 4 bucket waterfarm setup, with res, at 70 or less with one iceprobe, and poor insulation, in a room that got to 80F, lights on, under 1200w. Do not expect instant results. These are very small units, and will take hours to draw down warm water. At res change time, cool your water before swapping it out, with ice bottles, if you can. Makes the Iceprobes life easier. Be careful not to let it get too cold!!! A cheap alternative to the thermostat they sell, is a $5 mechanical timer, from Blowes. Play with off/on times, until you stay 63-68F. These units work great, within their limits. I think most people fail to insulate, and give these units a bad rep. A small fan blowing on the pwer supply will help make it live longer. If it fails, you can modify a pc power supply to run these, for about $5. Happy trails, hope that helps!