Dead algae?


Active member
Sep 22, 2020
Northeast Nebraska. Been an unusually cool spring with average high temps in the 60s. Opened pool 5 days ago. Water has been between 45 and 50 degrees. Vacuumed a few times so far and the brownish dust keeps re-accumulating in patches at the bottom of pool. They poof away with brush. We originally added some bleach but now are letting it drop back down to perform an ascorbic acid treatment. We fill with well water which is very hard water. We've added some Protech metal out plus, clarified and also some bioguard backup 2. With temps this low, could we be dealing with algae already? Or could it be dirt or pollen? Or could it possibly be iron from our water?


Mod Squad
LifeTime Supporter
Jan 17, 2012
Evans, Georgia
I would thinks its more likely pollen/dust.
Stay away from clarifiers, please. And that Bioguard Backup 2 is ammonia which will chew thru any chlorine you add until you've added enough to oxidize it. Another product we dislike.

Maddie :flower:


Active member
Sep 22, 2020
We're pretty sure we dealt with algae late last year when our pool was installed because we have massive amount of boatman and backswimmers. We ended the year with an extended SLAM but not sure we ever completed it successfully before closing the pool for the winter. Water was very clear when we opened this year but some debris on the floor. We also had several holes in our winter cover that allowed debris into the pool over winter.

We used the bioguard backup 2 this year as a preventative measure against another bug invasion which is our biggest fear. Several posts and product reviews claim it has great success against the bugs we've had. And so far, so good for us.

So is it possible we're still dealing with last years algae issue? Or leftover dead algae from last years SLAM?

We intend to add DE to our sand filter in the next week or so when it arrives. Hopefully that cleans up this fine dust issue we're having. If not, should we assume its algae continually dying?


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LifeTime Supporter
Jul 12, 2008
Seacoast, NH
Pool Size
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
Wish I'd taken a picture, but we opened to algae a about 2 weeks ago. The water temp was 48! SLAMing has been taking care of it. Not done yet because I miscalculated the CYA level at first. (Made the mistake of assuming my CYA was 0 when the test went all the way up to the top with the dot still visible. Added enough CYA to bring it to 30 and was SLAMing as if was 30. After a week, tested CYA and it was at 45 (AKA 50.) Apparently the CYA wasn't quite 0. So I was bringing the Chlorine up to too low a level.)

Bottom line, it is possible to have algae with cold water. It was no where near as bad as when we've opened later, but it was definitely algae. Nice and green, poofing when brushed, turning gray/white.
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