Phosphate free activated carbon 600g tub Polishes water, making it crystal clear Removes dissolved organics, medications, tannins, smells For freshwater, tropical and marine use Includes netting bag (15 x 20cm) Aqua One PremiumCarb is an activated carbon that is phosphate free and can be used in all types of filtration systems. PremiumCarb is a maze of microscopic pores produced by the activation process. These pores absorb minute particles held in suspension in your aquarium water. As the water passes through it the carbon "traps" the minute waste particles in its pores and consequently removes them from the water. Aqua One PremiumCarb is manufactured using the highest quality raw materials. As a result it is capable of quickly and efficiently removing dissolved organics and waste from your aquarium water. During its production the carbon is steamed, which enlarges the pore size and surface area. This process is referred to as activation. It is recommended to remove and fully replace PremiumCarb every 3-4 weeks to avoid releasing the waste back into your aquarium.