Is There Aluminum Toxicity in Freshwater Fish Tanks?

A healthy freshwater fish tank starts with quality water and safe accessories. By maintaining appropriate mineral and pH levels, and conforming to additional guidelines, you can ensure your fish live a long and happy life. Otherwise, the effects of metal toxicity, such as that created by aluminum dissolved in the water, can be devastating.

  1. A Little About Aluminum

    • Aluminum is the most abundant metal on Earth. Most Americans use it in some form everyday. It's found in groundwater, soil and rock, and it has many purposes. In small doses, aluminum may even promote growth in some species. But in water, especially acidic water, aluminum can become overabundant and may prove toxic.

    A Little About Water

    • Freshwater is water with low salt content. Tap water, meanwhile, can be full of minerals and chemicals used in the treatment process. Water can be "hard," or low in acidity with lots of minerals, or may be "soft" or acidic. High acidity allows otherwise insoluble aluminum to dissolve in water, negatively affecting fish.

    Aluminum Toxicity in Fish

    • When freshwater is acidic, its aluminum content tends to be higher. This can interact with the delicate electrolyte balance that fish have and can even cause fish gills to become covered with a slimy layer that makes breathing difficult. A shift in calcium balance caused by excess aluminum may also cause skeletal abnormalities.

    Maintaining a Healthy Tank

    • The first line of defense against aluminum toxicity is water testing. Test kits determine pH and mineral levels in the water. By adding or removing minerals through buffering, you can lower or raise the water's acidity as needed. Most freshwater fish thrive in a neutral pH level of about 7.0. However, a few species require a more acidic environment. Once you know and have achieved the correct environment, your local aquarist can help you choose aluminum-free accessories.