Black algae

[carnivalday]

Hi guys. Ive neglected my pool for about a year. Fortunately its still clear, but Im afraid I have some black algae. Black spots at the bottom of the pool, when I scrape them off they are dark greenish. Ran my tests, but my chemicals are over 2 years old. Ive ordered new, and they'll be here Thursday. And to add to my pool woes, the numbers on my SWG and pump have faded out, so I cant see where the pump and SWG is set at.

My CL level is 4, so Im assuming the SWG is doing its job. CYA is negligible, so I added a sockfull yesterday. CH is 300, TA is 70, so Im in the ballpark there. I know I need to get the CYA boosted up, but with me having to run the CL high because of the black algae, should I keep CYA at a lower level? If I boost the CYA to 40, I will have to set the FC between 7 and 16 to battle this black algae. At 40 its lower than recommended, but higher will mean a higher chlorine level for a while until I get this algae under control.

Thanks.

 

[PoolStored]

@Katodude is your resident BA expert...he'll weigh in...

 

[proavia]

I see that PoolMath is linked to your forum account - but the latest results are from 4 years ago.

How old are your K-2006C and K-1766 reagents?

Post a full set of current test results from your two test kits using non-expired reagents.
FC
CC
pH
TA
CH
CYA
Salt
Water temperature

 

[Katodude]

For Black Algae you are going to have to disrupt the surface of the algae physically. You can use a wire brush, which I dont like. If it is just a few spots put on a mask and snorkel and go into the pool and pick at it with a bamboo BBQ skewer.

If you have more than just a few spots, get in the pool with a weak pressure washer and you can use that to blast away the BA.

After you have physically disrupted the BA. You should dose it with LC. Get the strongest LC you can find and if the BA is close to the edges pour the chlorine down the side where it washes over where the BA used to be. If the BA is all over the place you can fill a 1 gallon pump sprayer and get into the pool and spray those spots. And yes you can do this all under water.

Then you need to keep your FC at 20% of CYA for the next several weeks.

 

[carnivalday]

Thanks, dude, I knew I could count on you. Will one of those garden gallon pressure sprayers from the big box stores work? Im not sure Ill have enough strength to push a pressure sprayer under water, but Ill give it a try. So thats straight LC in the pressure sprayer? Is it okay to keep CYA at 30, or do I need to up it?

 

[Katodude]

Yes, those big box sprayers work. Get the smallest one you can and fill it up. It will sink with you. Keep CYA at 30. You can also raise it a bit to make life easier on the SWG. Since you are not doing a full SLAM it’s less critical.