Hi. I'm new to the forum and I know this has been asked before but I just wonder if someone can clearly say whether the stuff in the picture is sand or algae. No matter how much algae killer or filtering of my pool there is always a fine layer of uniformly spread sand coloured matter over the bottom of the pool. I put my dolphin robot cleaner on fine filter and this is what came out . Is this sand from my filter or algae?
10.5 X 2m pool