First, a big THANK YOU to everyone that posted tips, hints, and constructive comments!
As you may have gleaned, I have 3 major problems:
1. Summer temps
2. Very, very hard water, at 700+ PPM
3. Too small a reservoir for my current, or future plants (14 buckets, headed for 20)
1) After receiving a lot of valuable comments on how to tackle the temp problem, I have done a lot more investigation of possible solutions. The problem lies in the BTU's injected into the uninsulated buckets, black connecting tubing, and to a lesser extent the reservoir itself.
To leave all that as is and try to cool the nutes down to 68F would take far too much energy for any practical and cost effective solution. 18,000 BTU's is simply out of reach by swamp coolers, ice bottles, mini-fridge mods, Peltier coolers, etc. And purchasing a water chiller to handle that load is far too expensive.
So my approach is to first reduce the heat load by insulating the buckets, tubing, and reservoir as much as is practical. Then I will determine, as best I can, the BTU's to bring that better insulated system down to 68F, or at least not more than 75F. That will, hopefully, give me a shot at a cooling system that is more practical and I can afford.
2) I should have tackled the hard water long ago, but wanted to see just how much of a problem it really was. While I have been able to grow a variety of veggies in it, the salts are still way too high. My choices are either try to use nutes designed for hard water (General Hydroponics has a hard water
nutrient), or solve the problem more completely by getting a Reverse Osmosis system. I have decided to go the RO way, as I can benefit from the better drinking water as well as provide a known good water source for my nute system. I will need to add some calcium/magnesium additives as well as standard GD
nutrients, but I believe this will be a much easier combination to work with and keep stable.
3) I knew early in the game that my 30 Gal reservoir would be undersized at some point. But, I procrastinated as I started adding more buckets, and just kept adding more water more frequently. That of course is not the best way to handle a good nute mixture. So I am now in the market for a larger reservoir that can be accessed easily for cleaning and that can be insulated. I may wind up building my own, but circumstances, availability, and high wood prices (even plywood) here in Mexico makes me look for some other way to do it. Finding stuff here is often a real challenge! Importing plastic barrels or 1-2 plastic 100 gal RV water containers from NoB are one choice I am looking at for a reasonable price. They look like they could be modified for cleaning access with a cutout.
So beyond insulating the buckets, lines, and reservoir and then throwing a lot of ice bottles at it, probably no further cooling methods beyond insulation will be attempted this summer. By next summer I should probably have a more appropriate cooling system in place as the ice bottle thing is a real PITA, LoL.
Monty