Tetra easybalance safe balanced water size 500ml refreshes aquarium water without the need for frequent stressful water changes replicates the action of a water change adds additional elements not present in tap water promotes the health and condition of fish and plants helps to control algae actively reduces nitrate and phosphate levels stabilises ph and kh levels adds valuable vitamins and trace elements to the water reduces the need for water changes to a minimum of once every 3 to 6 month