I, too, am an advocate of solar. It's free heat! Sure, it doesn't work when it's raining--but we don't swim then.

You don't NEED an automatic system if you set your manual valve(s) so it(they) are convenient. I turn them on in the morning before I go to work, and off when I get home, and don't use them if the water is getting too warm.

I had 96 deg water last summer...Algae is ONLY a problem if you neglect your water, not if you are checking it everyday--and adjusting as needed.