I went to clean a diffuser for a 7 gallon tank I'm putting together, as I'm pouring it I noticed how thick it was. At this point I'm passed the point of no return, so let it sit for 20 minutes. Rinsed and rinsed and rinsed some more, still smelled like bleach and it started foaming out of both sides of the ceramic. Needless to say, I had to toss it, especially after reading about other people accidentally using this stuff on purigen. Don't be a idiot like me and read the bottle before you use any bleach on your aquarium stuff. Good news is my garbage diffuser is now clean.