Green Pool..Need Advice (sand filter)

[akilpatrick]

Hello! This is my first time posting, but I have been having a difficult time with my above ground 18,000 gallon pool. I have been able to get it to blue-green color and even had it to where I could see the bottom. However, after vacuuming, algae bloom came back and my pool has been green for about 2 weeks now. I’ve shocked it and I did add stabilizer, but was told that I may need to partially drain my pool because my CYA may be too high. I’d love any advice on how to get my pool back in order. I did drain about 1/4 out of it today and re-added water just in case it may have been CYA.

Here are my readings:
Free Chlorine: 10ppm
PH: 7.4
Alkalinity: 90ppm

CYA: unclear since I only have test strips to test CYA. (Pic attached) Other readings were done with Taylor test kit

 

[mknauss]

Welcome to the forum!
You need to follow the SLAM Process Process. To do that, you need a proper test kit, see Test Kits Compared. I suggest the TF-100 Test Kit ™
While you are waiting on your test kit, add 5 ppm FC worth of liquid chlorine / plain bleach to your pool each evening with the pump running.

I suggest you read ABC's of Pool Water Chemistry and consider reviewing the entire Pool School eBook.