[pinballlooking]

Yes there are a ton of variables at this point. Input is welcome. Projects are always better with outside input. The people I tell about it around here could care less about the details.
The natural gas hot water heater (Emergency backup heat) I have on hand and I hope I don’t really use it. It is in the mix if we have a super cold winter and a week of cloudy days in the winter.

But it has the same requirements at the solar hot water heater I am setting up.
Today it will be close to 60 degrees outside the greenhouse will get close to 100 at the 5’ high. The fish water is 60. That is colder than I want it so today would be a perfect day to use the new heat exchanger.
The front grow bed is like a big radiator all the rock. The back bed will be so much better insulated.

I am thinking about getting tilapia again. If I do this will require the fish water to stay warmer. The heat exchanger will help keep them alive.
I completely agree with you some of this is just guessing on how it will perform in a complete season.
This setup can be used to cool the water this is a big plus if a heatwave comes over the summer.

It is ironic it seems like project is taking so long to get done but it also feels like a lot is getting done and changing all the time.