Slamming for long periods to fight black algae

Aug 23, 2013
Phoenix AZ
I have been a TFP voyeur for a couple of months now. I found this sight while searching for answers to Black algae solutions. I bought a TF 100 test kit. I drained my pool by 60% + to get my CYA down from the 100 level that it was at. I have been slamming for three weeks now. Water looks great and I think the algea is fading slowly. PH and alkalinity have been creeping up. I know the PH will read high during slam but should I reduce the alkalinity? The alkalinity was 100 when I started and the PH was 7.5. I think it is going to take a few months to rid this black algae as it was there for 6 or more months before I knew what it was. Do I really need to keep it at slam levels or just an elevated level and can I back off the pump from running 24/7? I have also been scrubbing with a wire brush every day. Current numbers are as follows.
PH 8.2+
FC 16
CC 0
TA 120
CH 320
CYA 40


Mod Squad
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TFP Expert
In The Industry
Apr 1, 2007
Sebring, Florida
Very good question. Since your pool is cleared up (right?) and you would likely pass an OCLT (right?) then I think I would simply elevate the FC (probably around 6-8 ppm) and continue to scrub with that brush.

The brush is the key to just need a little extra chlorine to make sure everything stays dead in your pool.

If your pH stays at 8.0+ when the FC gets below 10 ppm, then would be the time to lower it. Leave your TA alone for now...see what it tests after your FC gets below 10 ppm

Melt In The Sun

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TFP Expert
Oct 29, 2009
Tucson, AZ
Are you using a big wide wire brush, or a skinny one? I've found that a tiny brush works much better, since you can really rip into the spots rather than just scratching up the top of them. You need to be in the pool with goggles though, but in Phoenix it's probably still swimming weather, right?