Water enters the top of the degassing tank from the second mineralization tank. Here, the nasty gasses from the bacterial breakdown of the fish waste are removed from the water by aeration. As with the fish tanks, air comes in through the blue-green air hoses from an air pump to air stones at the bottom of the tank. The water (with the nitrate but without the nasty gasses) exits the bottom of this tank on its way to the raft tank. The black wire goes to a heating element which is also in this tank.