Aluminum Toxicity in the Aquarium
Ardan Huck July 10, 2002

At pH values of below 5.5 or above 8, aluminum can become toxic to fish. Some city water plants use aluminum sulfate to make the water clear in color, remove phosphates, and clear turbidity. If your pH is less than 5.5 or more than 8, you may want to check to see if your city uses aluminum sulfate. Some of the aluminum ions may remain in the water. You also want to make sure not to use any aluminum products for water or in the aquarium as aluminum will leech into the water. Some things that slow the leeching are organics in the water, oxidation on the aluminum, or plating on the aluminum, however, you will not know when aluminum could reach toxic levels for your fish. Soft water, as is often used for discus, can speed up the leeching of aluminum into the water.

Aluminum interferes with fish's respiration in the gills and they can die. If your pH falls in either of these two categories, and your city uses aluminum sulfate, you can combat the aluminum through the use of peat moss as it can absorb 80% of dissolved aluminum. This is best done in a holding tank to give the peat moss time to absorb the aluminum before using the water for water changes.

Carbon will also remove some of the aluminum, but there are variables, depending on the quality of carbon and the type of aluminum ion.

The best thing to do is to do is to make sure all water is in the pH range between 5.5 and 8.0 (if you are using water that has been treated with aluminum sulfate). Also make sure not to use aluminum products in the aquarium water (unless it has been specifically made for aquarium use and the finish is not damaged).

Sources from "DiskusBrief" magazines:
  • Vol II, March 1995 Issue 1, "The Significance of Aluminum Toxicity to the Aquarist" by Horst W. Kohler, Germany

  • Vol I, March 1994 Issue 1 "The Aquatic Toxicology of Aluminum" part 1 by Paul Ceroke, USA

  • Vol 1, June 1994 Issue 2 "The Aquatic Toxicology of Aluminum" part 2 by Paul Ceroke, USA

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