How did you dose it directly into your skimmer body? I tried taking the cap of my cup off and dripping it down the neck, but then my skimmer always goes crazy. I end up having to dose into my overflow box, but it doesn't reduce the phosphate anywhere near as much as I expect it to.Using Phosphate-E from Brightwell here.. used up to 10ml a day for a while but down to normally 1-2ml per day now on a doser. Never noticed any issues with my fish and have multiple Zebrasoma tangs which people claim are sensitive . For a while I dosed into a filter sock but gave that up and run it directly into my skimmer body now, have been doing that for the last few months with great success.