reneep,

if your stains are a brownish-yellowish color, I found the answer in another thread here. I had those stains also, everywhere under the water, sides, steps. I was using tri-chlor tablets at that time. Put some vitamin C (ascorbic acid) tablets in a sock, and wet it. Then rub on a part of the stain. If the stain goes away, here is the fix. Buy some ascorbic acid in a powder form. The label may recommend some sort of 'metal free' also. I added the proper amount of each for my size pool, and the stains disappeared in minutes. It was the metals leaching out of the water and grabbing onto the pool. Has not returned yet. I have switched to the BBB method. Good 'ol hurricane Alberto added about 3 inches of water to my pool last night and today, so that will help lower the CYA level, as I had to drain some off.