What Kind of Metal Is Aquarium Safe?

Older fish tanks used to have metal frames, which typically rusted over time, particularly if the aquarist used the tank to keep marine fish. Modern aquariums are constructed totally of glass or acrylic to prevent rust. Metals in general do not have a place in aquariums, although the rotors of submersible and other types of tank pumps still consist of magnetic powder. Aquarists sometimes use metals such as copper as medications, but certain fish or invertebrate animals such as shrimp and snails will not tolerate it.

  1. Aquarium Equipment

    • The rotor of an aquarium pump motor is a cylinder made from magnetic powder, mixed with barium and strontium. This ferrite material rotates at high speed on a steel spindle in the pump well and is in constant contact with aquarium water. The ferrite rotor does not create problems in water and is safe for aquarium use. Seawater is far more corrosive than fresh water, and a ceramic shaft typically replaces the steel spindle in pumps designed for marine use. Stainless steel shafts are sometimes used, but certain stainless steel alloys will rust in sea water. Stainless steel is safe for use in fresh water.

    Sensitive Creatures

    • Coils of aquarium chillers and elements of heaters often consist of stainless steel or titanium. However, you should exclude even these so-called safe metals from the aquarium if you are planning to keep mollusks. Cuttlefish and other mollusks such as octopus are highly vulnerable to metal poisoning when in captivity.

    Heavy Metals

    • Do not to use rocks that contain metals in the aquarium. Although it is unlikely, certain rocks can release heavy-metal pollutants in water. Avoid rocks that originate from mine dumps or watercourses downstream from them. Copper, zinc, lead and other heavy metals are dangerous to aquatic creatures in their free ionic form. In this form, the fish's metabolism will absorb molecules of these metals. Aquarium water with a pH of less than 7.0 activates heavy metals, which makes them toxic to fish. Pyrite, which has a brassy yellow metallic luster, sometimes exist in otherwise benign rocks, but will leach toxic metals into acidic aquarium water such as discus tanks.

    Copper

    • Copper cures a number of marine fish diseases and is of value to the hobbyist for this reason. Add this metal only to the quarantine or hospital tank, because it will destroy the beneficial filter bacteria in an established aquarium. Because the substrate and rocks will also absorb copper, don't house invertebrates in an aquarium that was once treated with this metal. Copper is generally toxic to all species of invertebrates and even to a number of fish species.