mike,you might try putting fert. in pond anyway.the reason i say this is i have added on to my lake several times and the water would get off color.every spring i go ahead and fert. the water anyway and it seems to help clear the water.my water would have about 8-12" vis. when starting to fert.however,i would not fert. muddy water but if water is off color i would go ahead and do it.