I'm not using RO water, I do have a GH kit I can use. My tap water is usually 3-4 drops. I'll check this tank. I dose around 1.5g of potassium nitrates once a week. I use the light EI dosing for this tank with KN03 and KH2p04 on Sundays and csm+b on Mondays and that's it. Not sure exactly how long they have been doing this but I have a 10 gallon dirted tank that the plants look the same and I do nothing but top that tank off and feed it. And I have not added magnesium to the tank