Thrive's take on the common coral plug is anything but common. These ceramic plugs look natural and are heavy. Unlike aragonite mixed with a portland cement, Thrive's coral plugs do not leach aluminum. Plugs are designed to organize, trade and not detract from the beauty of your aquarium. We have provided a hole and a Tyvex tag, so that you can easily track and organize your coral plugs. Tags can be written on with sharpies or underwater with a dark pencil. The shape of the plug is designed to ensure water flow to the base of the fragment, and to better blend in with your reef.