Algae, dead algae or dirt?

[Dan Morrill]

I will apologize now for the incomplete information in this situation. If a definitive answer is not available, I understand. I am posting for a friend. I have not seen the pool myself yet.

He has an above ground 10k gallon with sand filter and gas heater. Small gobs (coin sized or smaller) of dark brown almost black substance appears on the bottom. When you go to touch it, the substance "poofs" away and disappears. It only forms when the pump has been running overnight. If the pump is left off, nothing forms on the bottom of the pool.

He has elevated and held chlorine levels high (though not quite to SLAM levels) done many full scrubs, and replaced old stairs that had been harboring some algae. There is nowhere left in the pool to harbour algae to my knowledge.

Sorry I have no pictures right now. The fact that the stuff only appears while the pump is running is weirding me out and makes me think it isn't algae, but dirt getting in from somewhere? Is that possible without also seeing huge water loss? There is a small section of buried piping in his lines.

 

[halleys5]

I had that happen in my AG pool in the later years of its life. I am fairly certain it is a light algae bloom that is growing, dying, and being filtered out repeatedly. A good SLAM and vacuum/backwashing should help.
Any objects in the pool such as ladders with algae hiding spots should be taken out and scrubbed.
Also, adding some fine filtering media in the process can help depending on the setup, e.g. a handful of DE in a sand filter, filter socks in the skimmer basket, etc.

 

[reggiehammond]

I will apologize now for the incomplete information in this situation. If a definitive answer is not available, I understand. I am posting for a friend. I have not seen the pool myself yet.

He has an above ground 10k gallon with sand filter and gas heater. Small gobs (coin sized or smaller) of dark brown almost black substance appears on the bottom. When you go to touch it, the substance "poofs" away and disappears. It only forms when the pump has been running overnight. If the pump is left off, nothing forms on the bottom of the pool.

He has elevated and held chlorine levels high (though not quite to SLAM levels) done many full scrubs, and replaced old stairs that had been harboring some algae. There is nowhere left in the pool to harbour algae to my knowledge.

Sorry I have no pictures right now. The fact that the stuff only appears while the pump is running is weirding me out and makes me think it isn't algae, but dirt getting in from somewhere? Is that possible without also seeing huge water loss? There is a small section of buried piping in his lines.

Overnight Chlorine Loss Test to confirm if it's organic.
SLAM Process to eliminate it.

 

[jonhern]

I had this same issue, kind of ignored it last year since the water test were perfect, water was crystal clear and it just puffed away as you said from brushing or even just walking by it. After a little bit of use it was gone and mixed into the water. From everything I have read its was likely just pollen since it didn't happen on the walls, just the floor and was evenly distributed. Most people say to vacuum to waste but after trying it once and having it come back I didn't bother again since going near it makes it just dissipate into the water and not get sucked up, and skimmer sock wouldn't catch it all either and would get clogged so fast. But it kept adding up and this year it looked gross with all the pollen we had plus all the stuff from last year, so I decided to try something different.

This got rid of most of it but still a bit in the pool that settles at the bottom, especially after it rains, plus new pollen getting added every day. I have a sand filter. I back washed, and then added 2-3cups of DE filter to the skimmer. Vacuumed the pool floor, key to this is to go very very slow so it doesn't puff up into the water but up the vacuum hose. Once you start losing suction, do a long backwash of the filter to get all the DE and caught pollen out. Then do a 30 sec rinse, then repeat the steps until you finish the whole pool. My 30ft round ABG took about 4 cycles to get everything.