I use the water crystals and ONA concentrate in a decorative container as a all around de-deodorizer. They do make an ONA GEL, but for the price of a one pound bag of crystals and a quart of ONA concentrate, you can make about 15 pounds yourself, and you can use it over and over by recharging it as it drys out by adding concentrate mix. I do not place it in or near grow closet, but in living room , den etc. It lasts a very long time and the linen scent is great.