Phil,
I use the stuff Cecil told me about. It works very well and if you look at the total costs, it is in the noise. I go with best value and the 95% solution.
T3 is running well. With six days in a row of heavy clouds, the batteries were running on empty (29%). Ultimately, we took the second air pump off solar for a day. It was an interesting data point. The good news is that we lost very little heat that week (less than two degrees). The water is green and the quality is very good.
The Tilapia are putting on good weight.
Now I wait to see if they spawn.