When I set up my first tank in May, I was unable to find any pure ammonia. I made another attempt today without success (I now have another tank - its addicting lol) Anyway please be aware that there is "clear ammonia" but it still has surfactant in it. I don't know what surfactant would do to a tank but I suspect it would leave some kind of residue. Maybe this surfactant is some kind of ecological additive that is required in some states - I have no idea, but I just want to warn people that clear is not pure. I can't remember all the places that had it labeled pure, but three of them were Walmart, Walgrens and Lowes.