Quick Review Acids produce H + (also written as H ) ions in water Bases produce OH - ions in water H + + OH - → H 2 O An acid plus a base yields a salt and water. HCl + NaOH → H 2 O + NaCl

Neutral Water Neutral water is given a pH value of 7.0. It contains equal amounts of hydrogen ions (H+) and hydroxide ions (OH-). Dissolved chemicals and minerals change the balance of those ions from a perfectly neutral state.

Increase the amount of hydrogen ions (H+), and the water becomes more acid ("low pH"). Increase the amount of hydroxide ions (OH-), and the water becomes more alkaline ("high pH"). The further these values rise or fall, the more acid or alkaline the water becomes.

Acids pH = 0Battery Acid, Hydrofluoric Acid pH = 1Hydrochloric acid in the stomach pH = 2Lemon Juice, Vinegar pH = 3Grape fruit, orange juice, Soda pH = 4Acid rain, tomato Juice pH = 5Soft drinking water, black coffee pH = 6Urine, saliva pH = 7Pure water

Bases pH = 7Pure water pH = 8Sea water pH = 9Baking soda pH = 10Great Salt lake, Milk of Magnesia pH = 11Ammonia solution pH = 12Soapy water pH = 13Bleaches, Oven Cleaner pH = 14Drain Cleaner

There is no "normal" pH that applies to all fish. Because fish originate in ponds, rivers, streams, lakes, and oceans that have different pH levels, their needs are different. Saltwater fish prefer an alkaline pH of 8.0 or above. Freshwater fish thrive in a range lower than that, somewhere between 5.5 and 7.5, depending on the specific species.

pH can change over time, and even change in the course of a day. Typically it drops at night and rises during the daytime. pH will change as new fish are added or removed, as water is added or changed, and as the biological processes change in the tank.

Preferred pH of Common Frewhater Fish * Angelfish * Clown Loach * Goldfish * Harlequin * Hachetfish * Neon Tetra * Plecostomus * Silver Dollar * Tiger Barb * Zebra Danio

pH as it relates to Aquariums Acids are chemicals that lower the pH Bases are chemicals that raise the pH Buffers are chemicals that can 'tie up' acids or bases and keep the water at a specific pH. Different buffers will keep the pH at different values. Different fish from different habitats have different pH requirements.

How Important is pH? Changes in the pH, especially sudden changes, can prove harmful or even fatal to fish. As the pH rises it increases the toxicity of chemicals such as ammonia. It is an important factor to monitor during the break-in of a new tank. pH changes are particularly hard on young and sick fish. In a number of species of fish, breeding occurs only within a specific pH range.

Adding acids and bases can change the pH of your aquarium, but this can be dangerous. Wood in the tank or peat in the filter can gradually lower pH. Shells or coral can gradually raise it.

Buffers

Turn in pH worksheet at the end of class.