You are in good hands Ralph. Marie (mbar) helped me allot a couple of years ago and turned me on to the Vitamin C. I owe her much gratitude. I too have a Fiberglass pool and seam to have to treat my pool a couple of times each season. On another thread, waterbear has brought to light a yet unsubstantiated claim by a company (Water Tech I believe?) that a lack of calcium could cause problems in vinyl/fiberglass pools. No one is sure if this is true yet and I personally have my doubts but just for the sake of "research", would you post your numbers? Mine are as follows:

FC 3
CC 0
TC 0
PH 7.5
ALK 80
CH 60
CYA <30
Temp 84
16,000 gallon I/G Fiberglass

I currently have stains. My stains generally appear as grey lines running from one side of the pool to the other. They even appear as orange/yellow sometimes in certain light. The pool has been open for a couple of weeks now and the stains have progressively gotten worse. The last treatment was in August '05 and I'll be giving it the ascorbic treatment after the weekend. I'm trying to keep a log to try to figure out what is causing these stains and would like to compare others numbers when staining has occurred. I use a water filter (cheap RV type) when filling and have had my water tested for metals and there are no traces of Iron or Copper. Notice My Alk and CH are low? I'll be working on those after the treatment next week. I usually keep ALK between 90 & 100 and have never worried about CH but it has never been this low. I did do a partial drain when opening to get the CYA down and I guess the filter is working since no calcium seems to be added. Thanks in advance for your help.

Dave