RowaCarbon is a high-performance, high-quality activated carbon that contains an extremely low level of phosphate.Activated charcoal will eliminate in the aquarium, toxins and yellowing of water which will improve the health of your fish and improve the penetration of light leaving your water clear as crystal.The low-end coals are washed in phosphoric acid as in the final stage of their preparation and can release high levels of phosphate in water. Rowa Carbon contains extremely low concentrations of phosphate.Algal problems are often caused by the release of phosphate from activated carbon with high POI (phosphate production index), at a level, often as high as 14.0, which inhibits the synthesis of calcium Coral algae, corals and other bodies formed of limestone.