I'm a new pool owner fighting an algae problem.
The pool was built in the 60's and needs to be resurfaced. Because of that, the gunite is stained and it is difficult to discern the color of the algae that settles out on the floor. I have a sand filter w/ sand that was replaced about a year ago (before we purchased the home).
I have a LaMotte ColorQ for daily testing and a Taylor k155a FAS DPD I bought for SLAMing. I've been using software from Perfect Pool and Spa Pool Care Software with ranges aligned to the recommendations on TFP and the calculator here occasionally (mainly to calculate additions for SLAM b/c perfectpool doesn't want to deal w/ chlorine >10).
I can get the water looking clear, testing correctly in all ranges, etc. But when I run my Dolphin Nautilus Plus it kicks up a bunch of green algae and I have green in the vacuum filters. I can also brush and kick up plumes of green and turn the water into a green swamp. So I SLAMed following the instructions here....get back to clear, but still have the same issue.
I'm currently SLAMing now paying extra attention to the details...it's been about 5days. I have NOT been vacuuming to waste and have instead been brushing daily and backwashed the filter. The SLAM instructions say vacuum or brush once a day...I've chosen brush. I also added some DE to the filter per the instructions here (1lb PSI rise, etc) to hopefully speed the process. Current free chlorine is 15 and combined chlorine has shown 0 for two days on the Taylor test (assuming I am doing it correctly. 2 scoops, add chlorine until clear to determine free chlorine, add 5 drops of #3 reagent to same sample and it should turn pink but mine stays clear so CC=0). I haven't done an overnight FCL test..was waiting for the water to clear.
So here's my question: Should I let it all settle out and then attempt to vacuum to waste instead of continuing to brush and kick it up hoping the filter will catch it all? The only thing that makes sense to me at this point is the algae is dead, and the material is just too fine for my filter to filter out. It's hard to tell the exact color of the material due to the bottom color of the pool. It's definitely not white, it could be brown, but it certainly turns the pool green when you kick it up. Everything I read here, green=not dead but my CC of 0 would indicate otherwise (unless I am somehow screwing up the CC portion of the test but I don't think so).
I've avoiding vacuuming to waste just b/c of dealing w/ the runoff, loss of water, etc. but I think that may be the missing link.