We seem to have rusty tap water lately. The water tanks being in here for 24 years probably doesn't help. I've noticed lately that my snails like to stay above the water line. Could excess iron be the cause? Also my tanks have had a brown tint, and sometimes the tap water will come out brown. I also noticed rust spots on my laundry last night. This link www.idph.state.il.us/envhealth/factsheets/ironFS.htm seems to describe our tap water perfectly. The fish seem completely unaffected, but since snails are more sensitive to things like this I'm guessing it's the problem.