I keep mine at 0.07mg/l if not higher! as I stated before it all depends on what you are keeping-if you have alot of stiffs, I mean sps then alot of iodide is not good-get a test kit and adjust according to what you system uses. One drop would be absurd!!!!!!!!!! in my system but good in Chads system-but you wont know what your system requires until you test it