pebbletech

My Pool man said this is not black algae, but discoloration that occurs in old pebble tech finishes. Another pool man urges that is it black algae and can ruin my finish. My pool man is treating it in case it is black algae but it doesn’t seem to be getting better! What the heck do I do please?

Hello all, I am new here and really need some advice. I have a 15 year old 28' x 14' roman style pool with spa. It is ~15k gallons. I received quotes to replaster and they are pretty disparate. One company that admittedly doesn't have the best reputation quoted $8k to replaster with color...