Is Tri-chlor: Trichloro-s-Triazinetrione? Any guess as to how many I should use in my 15 x 30 AGP? I got one at HD and plunked it in the skimmer and it looks like it's just sitting there. I've only used BBB so have no experience with this stuff but it sounds like it was just meant for me in this situation. What gets most people into trouble with them?