pH Up is a liquid pH raising product for freshwater aquariums. By neutralizing acidic substances in the aquarium, pH Up effectively makes the water more alkaline. The pH may rebound down to the original pH depending on the level acid in the aquarium. Several consecutive treatments with pH Up may be necessary to adjust pH to the desired level, but if there are fish present in the aquarium, the pH should not be changed more than .2 in a 24 hour period. While many common aquarium fish will live in water with a pH of 6.8 to 7.5, a pH of 7.0 is ideal for a community aquarium containing a variety of freshwater fish. Live bearers like mollies and swordtails prefer a higher pH of 7.2-7.6. Acid-loving fish such as angelfish and neon tetras prefer a lower pH of 6.5-6.8. Making a partial water change (10-15%) will also remove some of the acids and help stabilize the pH. Adjusting the pH to the proper level will improve fish health, disease resistance, coloration and breeding.