Pardon my ignorance but I dont understand something about Seachem Purigen. I read some threads and the only thing I found is that the product is fantastic and works wonders in the aquarium. I would like to use it in my 90g since I noticed the water a little cloudy. I have the impression there is something in the water, maybe ICK because the fish makes strange moves and rubs against the decoration and gravels. Is Seachem Purigen a powder or gravel? How do you introduce it in the filter? Do I have to use a mesh bag? Where do you put it? In my 2217 I have ceramic rings and Seachem Matrix Bio-media. Please Ill appreciate your comments.