A submersible pump that runs 24/7 will add enough heat that you'll have to deal with it in some way.. You might get by with an additive to the water that lets you run your reservoir at higher than recomended temps.
I've got a little different take on Waterfarms and rdwc 5 gal buckets, and water levels, and pumps.. I use Waterfarms which are essentially the same thing.. I've modified my Waterfarms to recirculate their own water at about 5-6 gal an hour directly from the reservoir.. Gravity return.. No submersible electric water pump.. This mod is not difficult when using 5 gal buckets..
The only water pump used is the waterfarm drip ring itself, which is by definition, an air lift water pump.. They've been used for hundreds of years in one form or another..
This is where i'll get a lot of differences of opinions of what's the right water level.. It can vary by several inches, depending on who you ask.. At or one inch above the bottom of the basket works for me..
I maintain a constant water level throughout my small system by using a feedback reservoir.. With this type system, with the constant top down water movement, there will always be oxygenated water available in the hydroton that's submerged..
I'm not ignoring the fact that air pumps add heat to the air they pump. I've found that light air movement across the top of the hydroton seems to cool, by evaporation, the small amount of heat added by the drip ring water.. Oh by the way, no air stones either..
This is the reason you run your drip ring 24/7.. This waterfarm didn't recirculate. Just a dwc..
https://www.rollitup.org/t/pineapple-express-g13-labs-seed-to-harvest.344359/page-14 Post 273
Read this thread, at least the first 12 pages..
If you're interested i can link to posts of these modifications.
