400 Pro-Tip: Open the grey cartridge and lay both halves on the floor. Fill both sides with biomax, little cylinders standing up next to each other. Spray the full trays with water from a clean spray bottle. Place the trays in the freezer, careful not to spill out the biomax. Leave in the freezer for 10 mins. The trays will be frozen to the biomax. Now you can place both halves together without the biomax running all over the place. Insert in filter, a voila, you have a double layer of biomax.
Enjoy.
Enjoy.