Black Algae

Jun 25, 2012
I have a 18x36 29k gallon vinyl liner pool with a AutoClear saltwater generator. Last week the saltwater generator quit working. I suspect that the cell has reached it's end of life, however the system has been discontinued. I can get a replacement cell, but I didn't want to spend money on a discontinued system. I purchased a new CircuPool RJ45 which I will install this weekend. In the time being we have been putting chlorine tablets in the skimmer and everything was fine until the last couple of days. The water is clear, however we have begun noticing a little black algae growing on the liner. We tried brushing it but it will not come off. I told my wife to get some shock and shock the pool today. My question is that once I get the new SWG online, should the black algae begin to fade away? Any help would be greatly appreciated.


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Apr 1, 2007
Sebring, Florida
The short answer is "No". Black algae is difficult to get rid of.

That said, it is pretty unusual for black algae to even form in a liner pool and usually is the result of very long term neglect. I'm not sure that's what you have.

Anyway, You must shock the pool according to Pool School and then monitor your FC very closely and look for any signs of future algae. The SWG is actually much less capable of curing an algae outbreak than plain old liquid chlorine.
Jun 25, 2012
Thanks for the feedback Dave. Long term neglect should not be the problem. I have been bringing water samples to the local pool store and treating the pool according to their recommendations. The pool has been fine until just a couple days ago. The SWG had been out for about a week now and like I said, we have been putting tablets in the skimmer per the pool store's recommendation. I'll shock the pool per your recommendation.
Any guesses on what it could be? Like I said, it looks black and will not scrub off with a pool brush. It kinda looks like mildew which I wouldn't think would grow under water.
Jun 25, 2012
Butter knife is not an option. Although it is not a terrible algae bloom, there is too much there to scrape with a butter knife. We'll see what happens when I shock the pool.