What is the brown build up on an empty pools plaster?

Question

What is the brown build up on an empty pools plaster?

Answer 1

if there are trees around your pool then it is tree sap.the pool will have to be acid washed followed with a chlorine wash to get it all off and then that might not get it completely pool company owner eleven years experince

Answer 2

Probably mold and/or lichen.

Answer 3

There is a very strong chance that this is nothing but dead mold or algae. A strong chlorine bleach solution will probably clean it up. Be sure to leave it on long enough to do the job. Usually a few minutes will do. Then rinse thoroughly. You may have to repeat, as this stuff sometimes comes off in layers, the same way it grew to begin with.