Black Algae, Low CYA

[Bbp]

We found black algae in the pool. We scraped with a wire brush, brushed the pool and vacuumed.

FC :1
CYA : very low, the black dot on the bottom of the tube never disappeared.

Added three 120oz jugs of bleach. What should I use to raise the CYA? I have hth super 3" chlorinating tablets and hth super shock treatment.

Any advice would be appreciated.

Thanks

 

[Texas Splash]

Increase CYA by adding stabilizer/conditioner as follows:

Adding CYA:
To increase CYA via granular stabilizer, place the required amount as calculated by the Poolmath calculator into a white sock and place in the poolside skimmer basket. For those concerned about suction flow to the pump, suspending the sock near a return jet or from a floating device will also suffice. Best never to allow undissolved granules to rest directly against the pool surface. Squeeze the sock periodically to help it dissipate. Once dissolved, consider your CYA adjusted to that programmed (target) level. CYA test readings should show a rise in 24-48 hours, however some pools may experience a longer delay to fully register. Best to confirm final CYA in about 5-7 days before adding any more stabilizer/conditioner.

Once you add the stabilizer, use that projected CYA target to go to the [FC/CYA][/FC/CYA] and find out what your SLAM/Shock level should be for chlorine. Then follow the SLAM Process guidance. Make sure to lower the pH to about 7.2 before starting the SLAM. Good luck.
https://www.troublefreepool.com/content/180-Black-Algae

 

[Bbp]

Thank you

Pool math shows 30-50 range for CYA. Chlorine / CYA Chart shows 60*, 70, 80. What should be my target range for CYA? That copy paste is set for goal of 50 and current 10. 12lbs sounds like a lot. Can that be right?

CYA

Goal: 30 to 50

Add 187oz by weight or 195oz by volume of stabilizer or add 484oz of liquid stabilizer. To lower CYA you replace of the water with new water. Note: It can take solid stabilizer 24 to 48 hours to dissolve.

 

[Texas Splash]

Since you need to SLAM Process, keep the CYA low for now which will require less bleach (FC). SO aim for a CYA target of 30 if you can, then increase the FC to 12. If you overshoot the CYA to 40, then increase the FC to 16. After the SLAM, you can then increase the CYA higher as needed for your salt pool. Make sure to maintain that FC level, scrub those areas, and don't stop the SLAM until you pass all 3 SLAM criteria.

 

[mknauss]

Until such time as you have completed the SLAM and passed the three criteria, consider your pool a non-SWCG pool. You will be using liquid chlorine.

Once you have completed the SLAM process, then you an raise your CYA and use your SWCG for daily maintenance.

 

[Bbp]

Thank you for the responses and advice. I really appreciate it.

 

[Bbp]

How many times does the chlorine need to reach shock level? I have the CYA at 30. FC=12 last evening, now at 10. CC=.5

Thanks

 

[mknauss]

Maintain the SLAM level FC until you pass the three criteria as described in the SLAM Process article. Read it.

 

[AimeeH]

Hi Bbp,

Have you read through the article on black algae here: Pool School - Black Algae

Have you ruled out the potential black algae false alarms? This is a good read as black algae is kind of a different beast than the regular old green algae.

 

[Bbp]

I did read that, thank you. There wasn't a lot of the algae but I could pick off the outer cover and it was green underneath.