Effects of a Large Drop in pH on Fish
Ardan Huck July 11, 2002

Large drops in pH in a short period of time can cause the slime coat (mucous) to shed or fall off the fish in large "sheets". (Fischer, 1994) This can cause a loss of protection and partial loss of their immune system, rendering them susceptible to fungus and pathogens including parasites. Once the protective slime layer is gone, burns to the skin and fins are caused very easily by acid.

Another symptom can be respiratory problems as brown deposits form on the fish's gills. Oxygen can not get into the blood, and carbon dioxide can not get out of the blood. Ammonia can not be expelled from the blood either. The fish's blood becomes more acidic. This condition renders hemoglobin less able to bind with oxygen, so the "transport" of oxygen to the cells is also interrupted. The fish suffocate. Symptoms prior to suffocation can be gasping for air near the surface of the water, increased breathing rate, dark coloration, darting along the top of the water and even jumping out of the aquarium to try to escape.

This is why it is very important to make slow changes in pH, if you are even going to adjust the ph. Stability is important. Slow changes in pH are considered to be less than .5 to 1 change in pH per 24 hours. When adjusting pH and adding acid, once the "buffering" of the water is used up by the acid (by combining ions), the pH will fall very rapidly when adding more acid. Adjust pH very slowly before adding to the aquarium to allow time for the combining of the ions and the "pH bounce" (pH drops when acid is added, then it takes time for the ions to combine, and the pH "bounces" back up somewhat).

"DiskusBrief" magazine, Vol 1, March 1994, Issue 1, "Effects of pH Fluctuations upon the Health of Discus" by Roland Fischer, Germany. Translated by Paul Ceorke, USA

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