I know this is an older post, but this might help a new grower. A much easier way to keep your RDWC water temps down. Buy a used water cooler off kijiji or facebook market place ( $15- $35 ), one that you would normally put a 5 gal jug in the top. Now tear it apart so that you are left with the compressor and the cooling coil. Some of the cooling coils are coated in a protective plastic and some are not. If the one you have doesn't have a protective coating on it just wrap a plastic bag around the coil so you don't get any oxidation in your nutrients. Place the coil directly into your nutrient reservoir. Buy a device that will monitor your water temp. I use the Inkbird ITC-308 ($50). Plug the compressor into the cooling plug on the device and set your water temps and BAM Bob's your uncle!! I set my water temp at 67 deg and set the turn on temp at +2 deg (69).
