Hello TFP, I’ve had a home with a previously installed 12,500 gallon fiberglass pool for 4 years. The first two seasons I had issues with low PH, I tested for metals and had high iron. We then removed the pool heater and replaced about half the water. The iron went down but was still there so last year we drained about 2 feet of water 4 times (didn’t want the shell to pop out) and all levels were perfect. Now it’s time to open again and I have low ph, low alkalinity, and high CYA but no metals. What I’m reading here is that it’s from the tri-Chlor pucks. I’ve read that fiberglass has no acid demand like plaster does so my question is this: how do I use liquid chlorine? How much do I use and how often? Will the liquid chlorine be damaging for fiberglass? I live in AZ where it gets to 120, liquid chlorine honestly scares me but I see from all of you that the pucks just cause headaches. I’m planning on draining some water to get the levels normal and then switching. Thank you!