Hello TFP, put in this pool last summer. So far this year the swimming's been great, but after these last weeks of very high temperatures (water got to 88), I seem to be having an algae issue... or some kind of precipitant issue?
I have the frog "mineral" system, but have not been using it. I cut open several of the frog chlorine packs and fill them with trichlor tabs. The "mineral" thing is still in, never changed it and don't plan on it. Usually this "fancy chlorinator system" works well, but over the past few weeks, the chlorine level got quite high for no reason. Normally the pool can be run on low speed with a frog setting of "1" or less and chlorine stays constant around 2ppm. But for some reason the chlorine kept going up, so I set the frog to 0, and it still kept going up. It got over 19 and started looking hazy, so I took the frog chlorine pack out. Perhaps an o-ring failed.
An entire pack (a couple pounds worth) of trichlor was dissolved in just a few days. So that of course, raised the CYA significantly and lowered pH. Alkalinity is zero because the pH went down to 6.2, so I added soda ash to raise the pH, which burned off the TA. Then the greenish-brown sludge issue started. At first I thought it was mud from the kids, was somewhat stubborn to vacuum but I got it, cleaned the (dirty) filter, and thought things would be good. Put pump on high and it's been on high ever since.
The CYA was up to 85 and FC 15, the next morning the bottom had more patches of this greenish-brown sludge. Always in the dips and crevices. So I vacuumed/scrubbed it again (FC 15) and threw in a half gallon of 12% bleach. Much to my surprise, this actually made the issue worse! CC has stayed constant at 0, so it doesn't seem like anything is getting killed off. Vacuumed it again, next day, same thing.
So then I assumed that the CYA being so high must be locking up all the available chlorine, so I drained 4" or so and replaced with fresh water. CYA down to 60, but adding the rest of that gallon (FC 25) again did nothing (CC 0) and instead made the issue worse again.
At this point I'm grasping at straws. Was thinking perhaps it was a TDS/metal issue (possibly from the frog "mineral" thing), so I tried some metal-out, but it has had zero effect.
Any ideas would be very much appreciated. Is this even algae? Was going to fix the TA but no sense in doing that if I need to adjust the pH first.