weird algae like substance on bottom of pool

[patto]

just started workin at a brisbane pool which needs alot of work. one major thing i cant work out is there is a slimy sort of substance across the bottom of the pool. its a browny orangey colour. its able to be scrubbed off but it comes back within a week or so
the pool has a full tiled bottom. it seems to be covered in a slimy(ish) film. samples have been taken and sent to be tested by our local council and have come back inconclusive. the pool back in the day used to run with a copper clorination unit (not sure how exactly it worked or what its exactly called. ive never seen one before)
another pool in our area has the same problem and used to run on the same copper chlorination unit.

any ideas on what it is, what caused it, and most of all how to get rid of it???

[patto]

i posted here and not in the pool algae thread because test results came back negative for algae

[Guest]

Copper oxide?

The copper is rusting and then settling out of the water?

[chem geek]

Copper oxide is usually closer to looking black as shown here. Copper hydroxide is blue-green as shown here. Copper carbonate is green as shown here. At higher pH, there is more hydroxide and carbonate so at high copper levels both could potentially precipitate to produce a greenish mixture. However, I would not expect it to be slimy -- that's a mystery and usually indicates algae or possibly a lot of bacteria (biofilms).

If the water's pH is on the high side, then one can try lowering it to see if the substance dissolves. You'll probably have to do a water change or dilution to remove it, though if you are able to redissolve it then a large amount of metal sequestrant could keep it in solution, at least until it gets diluted eventually through subsequent water change.

Browny-orange sounds more like it could be a form of yellow/mustard algae (see this link for a photo). This usually forms on the shadier side of the pool and is somewhat like dust that moves easily (i.e. doesn't tend to stick). Strange that the test showed it wasn't algae. Also, if copper levels are high, then algae is unlikely.

Richard