My fiberglass pool was all brown. I managed to remove all the stains with iron eraser. I have read many posts on this forum and have taken lots of notes. If I am correct I think I need to keep my chlorine and ph on the low side and keep my calcium on the high side so these stains do not return. I also need to put in a sequestering agent so the metals stay in the water not my walls. Please someone tell me what you think about what I think I learned from all my reading.