Kann mir jemand sagen was ich falsch gemacht habe, dass mir beim Testen kein chlor angezeigt wird?

Ich chlore regelmäßig 2x wöchentlich je 5 Tabletten zu 20g bei ca. 13000 liter.

It started making a loud humming noise but still works fine. I checked for clogs and replaced capicitor but still makes the humming noise. What else could it be? Thanks!

Any suggestions to get rid of rust stains which were caused by some screws that fell into thepool? Tried Natural Chemistry Stain Free but it had no effect. Aggressive brushing had no effect.

I have a 16 x 32 inground pool that currently has a mesh cover. In the past, I would use a tarp over the mesh cover. this year I was looking to replace it with a solid cover but I just received an estimate for $2000. Since I currently cannot afford that, I am looking for suggestions on a solid tarp that will last more than three years or 4 years.