Fiberglass pool discoloration

[Jeanniemac823]

Hi,
I maintain a fiberglass pool that started to discolor in August. Testing indicated NO Iron and .3 Copper. A second test, poolside, using a metal testing granules from Bioguard did nothing to remove the stains when using the Copper treatment, BUT! using the Iron treatment the stains dissolved instantly. We treated the entire pool, then used a metal sequester, initially, the entire bottle and for 2 weeks since, maintenance doses. IT"S BACK! It's starts out rusty but gradually goes to a greyish black. There are rocks around the pool including a waterfall and newly placed small river rocks. The landscaper said they were loaded with dust when they put them down, right about the same time it began to turn. Anyone have experience with [i][i][b]manganese problems in pools? Could this be caused by either the new rocks or the existing rocks from the waterfall, overtime (4 years) leaching minerals into the pool? I need help ASAP! HOMEOWNER IS FUMING AND I"M SUPPOSED TO GET AN INSTANT CHEMIST DEGREE! HELP!!! Email me! jagmac3@msn.com