Black spot on bottom of pebble tec pool


New member
Apr 4, 2018
Tucson Az
Hi there,

My in ground Pebble Tec pool is 15 years old. A black spot has appeared at the bottom of the pool. I tried scrubbing and applying chlorine to the spot but nothing has changed so I don't think it is black algae but not really sure ?

I have attached a pictures and hopefully this will be of some help!

Thank you so much,



TFP Expert
LifeTime Supporter
Jan 4, 2016
Sydney, NSW, Australia
Welcome to TFP! Good to have you here :)

Try brushing it, then put a trichlor puck on it for 5 minutes. Then brush again, and put the puck over it for another 5 minutes. Then take the puck out of the pool. Check it in a couple hours and see if the dark spot has lightened up.

Don't leave a puck on it any longer or it may lighten the plaster.