Replacement Activated Carbon for all JBJ 28 Gallon Nano Cubes and JBJ 30 & 45 Gallon Rimless Aquariums. JBJ recommends you replace your carbon monthly. Our Bio balls are 100% polypropylene making them a safe reliable biological filtration media for fresh and saltwater. They are manufactured for use in koi and water garden ponds, freshwater fish tanks, saltwater aquariums, aquaponics, fish hatcheries and much more. This is great for you because you will have a clearer, odor free aquarium while the exceptional water quality will help your aquatic friends thrive. Our premium carbon makes rinsing easy since we clean and wash out a majority of the dust and fines.