03-22-2010, 01:10 PM
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Caution on using baking soda (sodium bicarbonate) to raise pH
The use of sodium bicarbonate, i.e., plain baking soda, to raise pH was mentioned in one or more threads recently. In doing some research on Mimagoniates, a family of characins the reproduce with internal fertilization, I came across some pertinent information on the use of sodium bicarbonate in the second of several articles authored by Stanley Weitzman, Lisa Palmer, Naercio Menezes and John Burns, dealing with the preparation of suitable water for forest-adapted fishes. The article recommends methods used to adjust hard, basic tap water into soft, acidic water suitable for fishes requiring such water. The authors provide a caution on the use of baking soda, and below I am citing the relevant passage verbatim.
Sometimes in an emergency, when the pH becomes too acid and we are temporarily out of reverse osmosis water, we will slowly adjust the pH with a dilute solution of sodium bicarbonate, bringing the pH level from 5.5 to 5.7 over a period of an hour. Usually 24 hours later the pH will have again turned somewhat more acid than pH 5.7 and we will adjust it further, to a pH of 6.0, with a small amount of sodium bicarbonate solution. However, sodium bicarbonate has no effective buffer action and cannot stabilize pH in the face of additional acidic waste products. Also, one must not continually add sodium bicarbonate to adjust the pH because eventually the sodium ions present will reach intolerable levels. Adding a buffering solution that contains ions of calcium or magnesium of course produces undesirable hard water. There are commercial pH buffers sold for soft water use. These are sold primarily for use in caring for and breeding discus, which also need a soft water environment. These buffers may be quite suitable for controlling the pH of soft water and not affect the sperm or fertilization of externally fertilizing fish species. However, we have not used any of them, preferring to adjust the Ph in a more "natural" way by exchange with freshly prepared soft water. [my emphasis]
This article, entitled Maintaining Environmental Conditions Suitable for Tropical and Subtropical Forest-adapted Fishes, Especially the Species of Mimagoniates (Part 2),
appeared in the July 1996 issue of Tropical Fish Hobbyist. Part 1 of the series discusses the specific water parameters required to maintain the long-term health of soft acidic water forest fishes, and the second part describes their recommended method of doing so (which happens to be RO).
At the time of the articles (latter 1990's), John Burns was a member of the Department of Biological Sciences at The George Washington University, Washington DC; Naercio Menezes was a biologist with the Universidade de Sao Paulo, Departamento de Zoologia, in Brazil; and Lisa Palmer and Stanley Weitzman were members of the Division of Fishes, Department of Vertebrate Zoology, Smithsonian Institution in Washington, DC. Dr. Weitzman is (currently) Honourary Research Scientist at the Smithsonian, and is unquestionably the foremost authority alive on characoid fishes.