Heavy Metals

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Fish - Safety

Heavy Metals

It's common for domestic water supplies to contain varying amounts of metal. Iron, lead, zinc and copper are particularly associated with soft waters. Because soft water is more soluble, it has a higher corrosive action than harder waters. Salt water is very corrosive, so try to avoid placing any exposed metal items in your aquarium.

Copper is more soluble in soft water and can pose a real health risk to your fish. Look for gasping, coughing, color changes and cloudy eyes, which could all indicate metal poisoning. Diagnosing metal poisoning in fish is extremely difficult. It involves tissue analysis and microscopic examinations, since fish can store heavy metals in their tissues at levels many times that found in the surrounding water. Different species of fish will have different tolerance levels for exposure to heavy metals. Heavy metals include:

Lead
Zinc
Cadmium
Copper
Silver
Gold
Mercury

Run the tap before using the water, and flush out all hoses to get rid of toxic plasticizers which can occur in the standing water inside the hose. If you don't have time to wait for the tap, there are chlorine neutralizers available that also remove copper, lead and zinc from the water.

Copper

This metal in saltwater and reef aquariums is toxic to fish and invertebrates. The basic rule is don't use it at all. In freshwater applications, copper is frequently found in medications and tank treatments. Fish have a very low tolerance for copper, and levels must be monitored carefully. Be careful with:

Copper Pipes and fittings. These don't have any place at all in use around your tank, especially if exposed inside the tank.
Treatments and medications. Unless you have no other options, treat sick fish in separate treatment tanks. Many medications contain copper, and some species of fish can become gravely ill or die if exposed to any copper at all.

Iron

Not listed as a heavy metal, it's worth mentioning here because it's a common metal in your water supply, and like lead and copper, you should test for iron since your fish have low tolerance levels to it. Because of rapid rusting, iron decorations should never be placed in your fish tank.

Lead

The most likely way lead will enter your aquarium is through the water supply coming through your own home's water pipes. Running the tap for a few minutes helps lower lead levels, as will using a neutralizer. Test kits are available to monitor your tank's metal levels. You can also introduce lead into the water via:

Your tank decorations. If you've used your own, the paint may well contain lead, as will some plastics and rubber. It's safer to use natural decorations, or better still, buy aquarium-safe products.
Mosses and plants. Mosses tend to retain heavy metals, particularly those originating from Eastern Europe where acid rain has polluted the lakes and rivers.

Mercury

Mercury is a renowned poison in fish because of its ability to penetrate the skin. It is more of a problem with fish you'll find on the dinner table than aquarium fish, but you should be watchful for its presence. It can be found in:

Cleaning Products. Some household cleaning products do contain mercury, so read labels carefully or buy an aquarium-safe cleaning solution.
Thermometers. These all contain mercury. Check your thermometers for cracks and leaks as part of your maintenance procedures.
Electrical Equipment. Mercury is frequently used in the manufacturing process. Discard and replace faulty or damaged products used with your aquarium.
Your tank decorations. If you've used decorations that didn't come from an aquarium supplier, chances are the paint may well contain mercury, as will some plastics and rubber. It's safer to use natural decorations, or buy aquarium-safe ornaments and decor.

Zinc

As with lead, the most likely way to introduce zinc is through the water supply, but there may be other things you may not be aware of. Watch out for:

Your tank decorations. If you've used decorations that didn't come from an aquarium supplier, chances are the paint may contain zinc. It's safer to use natural decorations, or buy aquarium-safe ornaments and decor.
Mosses and plants. Mosses tend to retain heavy metals, particularly those originating from Eastern Europe where acid rain has polluted the lakes and rivers.
Zinc oxide medications. Calamine Lotion and Desenex are zinc-based human medications. Always wash your hands thoroughly or wear gloves before working in your tank.