A home swimming pool contains 145 m3 of water. At the beginning of the swimming season, the water must be heated from 15 to 32°C. How many joules of heat energy must be supplied?

I have an in-ground swimming pool, and there is algae stuck on the walls that I can’t scrub off. I went to Home Depot and they told me to balance out the pH, TA, etc. Then I put two 3″ chlorine tablets the feeder and left it there overnight. It doesn’t look like it dissolve or anything. It is safe to continue putting in the shock and algicide? And afterwards, if it is still in the feeder, is it safe to swim with it in the pool?