I'd say about a month until I received mine... I didn't know what was on my acros, all the research I did and Pictures I saw nothing looked like what was on my one acro colony. But I still purchased it and I used a half tablet. What I did was take one of the tablets, cut it in half and smashed in into a very fine powder. After that I dosed that powder (mixed with a small amount of tank water) 4 times over a week. The only thing I noticed was my skimmer went a tad crazy, but i just emptied it. After the week, I added new carbon and turned my reactor back on and did a water change...to this day have not seen any critters walking on my acros and all PE is back to normal as with the colors.