Rubber type growth above waterline, what is it??

[johnnyk]

You could also try to remove the "rubber" with baking soda and water. Sprinkle a bit of baking soda onto a damp cloth and rub. Did magic for me. Be careful not to get too much baking soda into the spa water as it might mess up your chemistry.

[Scuttler]

You could also try to remove the "rubber" with baking soda and water. Sprinkle a bit of baking soda onto a damp cloth and rub. Did magic for me. Be careful not to get too much baking soda into the spa water as it might mess up your chemistry.

Thanks....pretty sure that was one of the many things tried but to no effect. It's like a glue. The xylene softens it so that if can be scraped off but once it dries it goes to rubber again. I now have a tennis ball sized pile of rubber 

[johnnyk]

Ok, so my next suggestion would be a hammer and a chisel

[Scuttler]

Ok, so my next suggestion would be a hammer and a chisel

 

I was looking at the circular sander with a buffing pad