I test my water using the api master test kit. (And yes I shook the crap out of it!) I'm currently dosing flourish comprhendive in my 20 gallon long low tech. Stocking is at about 70%. I'm feeding a pinch of flakes in the morning for my black neons and 2-3 sinking wafers for my cories. At night I drop one algae tab in for my otos and nerite snails. I heard that nitrates should be between 10~20 ppm. I have been continuously testing 0 for the past month. Even my previous 10 gallon tank (running for 6 months) always tested at 0. What am I doing wrong? Only one or two yellowish leaves on my anubias. Otherwise the tank is doing great.