We have an 8 year old gunnite pool with a dark gray speckled mini pebble plaster finish.
To the touch the finish is perfectly smooth and free of cracks or chips, and bonded tightly.
My pool guy uses tri-chlor or lots of the 3" tabs in the skimmers and he says he keeps the chlorine level at around 5-10 ppm, we still have persistent algae forming on the bottom and occasionally on the sides every 4-5 days. I have not tested the ppm to be sure he is correct.
Pool guy swears there is a problem with my plaster and he says it is slightly porous and allows the algae to hide and grow in the pours. He takes care of about 20 pools and says mine is the only one with persistent algae. He's been doing pool care for a long time.
I have seen him use the wire brush along the bottom and he can create a grey cloud apparently coming from the plaster while he is brushing, and that worries me some.
Anybody had experience with this kind of pebble finish and had a recurring algae problem?