Here is a totally different way to approach the same problem; aquaponics. These systems typically run at their best in the low to mid 70s F, which is as much as 20 degrees warmer than many people target for their RDWC. Being a hybrid between classic hydroponics and fishkeeping, where the effluent of one system is a prime input for the other, the ultimate source of nutrients for the plants becomes... high quality fish food, processed by both the fish themselves and an active living biofiltration system. The water recycles continuously, only needing replacement should salinity climb (so top off with RO to maximize this interval).
I'm thinking very hard about using a system much like this to not only feed my plants and grow fish, but also as a temperature management system for both my op AND my home. Almost a kind of fishy/planty/grow op-py heat pump, to reduce or replace the need for either external source heating (gas for house, electric tank heater for fish) or compressor based cooling (AC) for house and growrooms.
If it's possible, it would replace expensive hydro store nutes with fish food. It would keep all of the water for both plants, biobeds and fish temperature managed without the need for chiller- except perhaps in extreme circumstances- and because I plan to dump as much heat from the bloom rooms into the water as I can, I will reduce (and during favorable weather conditions, eliminate) the need for water chilling/actively cooling the op and eliminate the need to heat an outdoor fish tank throughout a Colorado winter. Save money on cooling, save money on heating, save money on nutrients... and free fish.