Dosing ports are on the opposite side of the sample tube. It goes into the last chamber on the left side and straight to the return. Sample tube is in the far right chamber with the overflow. I stopped dosing right away once I saw the high readings. Have not dosed since. Tank looks fine, no precipitant on my substrate or other equipment. My hammer looks more full. Kenya tree and Xenia look great. I have 2 of 3 Acans that receded back but are still holding on. The third acan is fluffy but you can tell it pulled back some. My purple stylo is what took the hit. Bleached and no polyps on one side. Other side is half and half. Inverts are good as well as the rest of the live stock. I have a salifert test as well as Hanna checker. I will perform test using both units and compare.