Have you seen or tried these ammonia sucking gravel in your aquarium? They have a gray color and are made by a company called A ZOO. If you have any knowledge or experience on them please poste here. Thanks.
It's probably zeolite. It holds ammonia. The only problem is that it can only hold so much then you have to change it out. Also, a drop in pH can cause it to release the ammonia back into your tank.
