Also I have been battling what I thought was mustard algae but could be tree pollen. I have a giant 100yr live oak in my front yard and a massive pecan in my backyard by the pool. So I’ve been battling this for months now and have spent a small fortune on chemicals. But I noticed the other morning after the pump wasn’t running that it was not on the bottom. So I backwashed and rinsed twice. Turned my filter back on and a few hours later it was back. I then got in the pool and made a whirlpool and got it all stirred up. Let the pump run for a few hours and killed it. Next morning nothing on the bottom. I turned the filter back on and a few hours later it was back. Could this be something that is just bypassing the filter? Why is it not there when the pump is not running?
Just a guess, but it sounds like dead algae to me. The flow of water across the pool bottom (when the pump is running) allows the dead algae to "pile up" along creases and in low spots. Pump not running the dead algae settles to the floor in a layer too thin and uniform for you to see it.
You probably need to SLAM the pool but you must post your current test results so we can see where you are. What does your water look like now?
Do you have a pool vacuum? You could run it for a couple hours when you can visibly see the stuff on the bottom and it should suck it up and remove it from your pool. If it comes back then, its algae. If it doesn't come back, probably dirt/clay. I had what I thought was algae in the creases of my liner when I opened this year, except every test pointed to no algae and the water itself looked perfect. Turned out it was just dirt and clay that looked a little brown.
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Also, can you add your pool stats like equipment, size, accessories, etc to your signature?
I do have a vacuum and I do run it. It will pick it up but then come back a few days later. Just wondering why it isn’t there with the pump not running. Pump has been off now for 48hrs as a test and it’s still not there.
The only reason I want to slam is because I have been battling this algae or whatever it is on the bottom. It just keeps coming back. Been dumping in yellow stuff algaecide and pounds and pounds of shock. Goes away but then comes back. May have been from the 130+ CYA reading though.
Now that you have your CYA in check, don't put in any more shock powders or hard chlorine. Stick with liquid chlorine so your CYA won't climb back up to where it was before. Also don't use any more algaecides. They are only a preventative. They won't do anything if you already have algae, and they can have adverse affects with ingredients that could harm your pool like copper.
Go ahead and SLAM your pool. Bring the FC up to 24 and follow the SLAM procedures. If your water is clear, it shouldn't take too long. Once you think you maybe be done, you should perform an OCLT to verify that you aren't losing any FC overnight.
Brush the walls and pool floor plus any nooks and crannies where algae could be hiding like a pool light or stairs. Test the FC every couple of hours and when it drops below 24, redose it back to 24. Rinse and repeat. POP (pool owner patience) is a must. Let the SLAM do its thing.