Recurring black dust

[Bnelson]

I keep getting this black dust. it settles on the bottom but when I vacuum or sweep it it just disappears for a short time then comes back over night.
This is very annoying. Tried vacuuming to waste, no good. Tried Shock with bleach, no help. HELP!!!

[aylad]

Do you have any idea where black dust would be coming from? Have you looked at it out of water to make sure it's black, and not maybe rust or brownish? Any large-scale fires or heavy fertilization of crops going on in your area?

If you could post a full set of numbers including FC, CC, CYA, Alk, and pH, as well as what chemicals you're using in your pool, as well as what kind of pool it is, it would help us to help you figure out what it is and how to make it go away.

Janet

[Bnelson]

It is brownish not black. It totally disappears when the water is stirred up but settles back when water is calm or overnight. I try vacuuming it up but just reappears, again, again. I just opened pool but this was a continuous problem last year. Working on getting pool adjusted with 12% chlorine and pucks now, going to add some polyquat if I can find it, or algaeside. Would LOVE to solve this problem.

Pool is a SPLASH SUPERPOOL 17x29 4' above ground. Will post readings Thursday. Just dumped 5 gal of 12% liquid chlorine in and have pucks to help raise level fast.

[aylad]

It's possible that it's mustard algae, in which case it will grow on the bottom and up the sides of the pool. If that's it, then you'll need very high shock levels sustained for a longer period of time to get rid of it. In order to know how much chlorine you need to sustain, you really need to know your CYA level. If you're using algaecide, then you're wasting your time to shock first, since the algaecide will deplete your chlorine rather quickly. As algaecide is much better at preventing algae than killing it, I would wait on the algaecide and just sustain a shock on the pool until you're no longer losing any chlorine at night. If you'll measure your chlorine at night after the sun is gone, and measure it again in the morning before the sun hits it, you'll get an idea of whether there's any chlorine loss in that time period, and if so, you know it's something in the water that needs to be killed. Sustain your chlorine at shock level (again, that's dependent on your CYA level) until you no longer lose chlorine overnight.

If you're not losing any chlorine overnight, and if it is only on the bottom and not the sides, then I would suspect either pollen or sand that has blown in and sunk. The only thing you can really do for pollen is stir it up really well into your water and use a slime bag on the basket to catch it. Might also want to check and see if it's sand, maybe being blown back into the pool from a broken lateral in your filter.

Hope this helps!
Janet