^Hey my rez temps stay about that high too and instead of rez chillers I invested in better pumps and airstones to raise DO. In addition to the Hygrozyme and Roots Oreganum XL (similar to Hydroguard, different brand), I use one XP-125 pump and three 5" donut airstones for each 12 gallon tub that houses three plants. Each pump has the two outputs running on the same line by way of a t-valve, and that single line is run through a 3-way gang valve with each of the three lines hooked up to its own 5" Donut airstones. All of the above are Topfin brand and available at the large commercial pet store in my area. My seedlings had root rot, but once I put them into my DWC tubs the root rot has been cured and I'd say my root growth is comparable to those found in aeroponic systems and my rez temps hold around 75-78 degrees.