Avoid fish loss due to low oxygen without the need for an air pump. These stones use a harmless chemical reaction to create oxygen without excess bubbles for up to one month and are safe to use in freshwater and marine aquariums. Ideal for using during power outages, while transporting, in goldfish or betta tanks, and more. Use only bottled spring water (not distilled water) at room temperature. Place gravel in the tank. Put stone piece(s) on the gravel. You may see air bubbles forming on the stone, that is the oxygen generated by the stone. Those air bubbles will disappear, dissolving into the water. Continues to produce oxygen for the period of about 1 month.