Algae is dead but it won't settle

[Kevin from LI]

I had a green algae bloom and checked the chemical readings before slamming it. PH 7.3, TA 80, CH 100, CYA 50, FC 4, CC 0, water temp 80. Added bleach to bring FC up to 25. PH went up as expected close to 8. Brushed and brushed. Ran the filter. Checked with a DPD kit (a Taylor kit that only reads FC and PH). Checked in a couple hours and FC had gone down to 22. Next morning FC 20. Next morning 18. This was a few days ago and now FC down to 10. There is no biofilm or slime anymore, but the water is a lovely cloudy aqua color, and we can't see the bottom.

The robo cleaner picks up some greenish/brownish sediment. I was hoping all the dead algae would settle and I could vacuum it out to waste. But it isn't cooperating. Do I need to keep the shock levels up high for longer? And will it hurt the robo cleaner to run in such harsh conditions?

Thanks

 

[Texas Splash]

Hello Kevin and welcome to TFP. Yes, you need to SLAM (not shock). I believe there is a misunderstanding of what SLAM is. TFPC methods do not simply "shock" or "super-chlorinate" a pool as typically advised by the local pool store. We do what's called "SLAM". SLAM is significantly different than an overnight or short-term “spike” in chlorine, and can take a few days (perhaps even a week or two) to properly complete. The recommended test kit is extremely important to properly conduct a SLAM. TFTestkits.net

Pool School - SLAM - Shock Level And Maintain

We “Maintain” a SLAM until 3 objectives are met:
1. Water is clear
2. You do not lose any more than 1ppm of FC overnight (that's the OCLT)
3. CC (Combined Chlorine) is <.5
** You MUST meet ALL 3 items above to properly do a SLAM. Simply “spiking" the FC higher than normal isn't SLAMming, therefore there’s a good chance your algae will return.

At this point, I suspect you are simply stirring-up a bunch of algae that is part dead and part alive. Follow the SLAM page carefully and you should have no problems eliminating the cloud and green from your water.

Good luck!

 

[Kevin from LI]

Thank you... Texas? I must've forgotten the "And Maintain" part of SLAM.
I see it starting to clear up now.
Oh yeah - Can the high FC damage the robo cleaner?
I hope I can keep using it since it's taking out alot of dead algae.

 

[Texas Splash]

As long as your FC and CYA are in-line with each other as noted on the Pool School - Chlorine / CYA Chart you and your pool equipment are fine - even at SLAM level. Good luck, and "maintain".

 

[tim5055]

I'm confused, you state

Checked with a DPD kit (a Taylor kit that only reads FC and PH)

DPD test kits only test to FC 10. How are you getting your readings - or am I as confused as my wife says?

 

[Kevin from LI]

Hi Tim - yes, it's a method I found on a US Army website. My kit reads to 5ppm. I measured the capacity of the vial (6ml) and began by dividing it in half. I put in 3ml of distilled water and 3ml of pool water. Then whatever reading you get on the color scale, you double it for the actual reading. To get to the point I could read 25ppm (current), I had to do a little more math. I divided the 6ml vial by 5, came up with 1.2 and worked from there. So I measure 4.8ml of clear water and 1.2ml of pool water and mix it. Then if you get a reading of 5 on the scale, you multiply by 5 to come up with the result of 25ppm FC.
I'm planning on going to Leslie's later and get a new reading on the CYA to see if the FC has to be even higher.

Thanks