Ive been useing it for about 1 year with no prblems in all my tanks. I collect at an inlet on incomeing high tode only, try to do it on AM high tides only. If the water looks funky I pass for the day. I run it through a 10" houseing with a standard sediment filter and then through a filter sock while filling the tank. I also let it sit in 55 gallon drums for at least 2-3 days and then do a change on one of my small tanks first as a test. I know several LFS that do it as well but you may want to check with local reefers to your area to ensure there are no pollutants common, for example farms near where you want to collect may release fertilizer runoff. Do some test and you should be fine, but like anything it is a gamble. After 1 change and watching my coral perk up I decided it was the right thing to do.