Copper is an important trace element.
Copper is an important trace element for animals and plants. Animals have copper e.g. B. in hemoglobin. Plants need copper for photosynthesis.
Copper sulphate is a well-known remedy against algae, insects and some types of fungi. Years ago it was recommended to use copper against hydra and to put a copper coin in the aquarium to prevent parasites. In the meantime, attitudes towards copper have changed. Presumably more fish were killed than saved through the use of copper.
The Harmfulness of Copper
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Copper is a heavy metal and above a certain level it can be harmful and even fatal to many aquarium inhabitants. Catfish and invertebrates, e.g. B. shrimp, on copper in the aquarium water.
Filter bacteria also do not tolerate copper well, so that large amounts of copper should not get into the filter.
All plants require copper in the smallest amounts. But for some plants larger amounts are very toxic, while other plants can tolerate a little more copper.
Because people are relatively insensitive to copper, the toxic effect on fish is often underestimated. There can be levels of copper in tap water that are harmless to humans but can kill fish.
Copper is from approx.
- 0.03 mg/l harmful to algae
- 0.08 mg/l harmful to aquatic plants
- 0.10 mg/l harmful to fish
- 3 mg/l harmful to humans
The toxicity of copper depends on the number of free Cu++ ions. As long as the ions remain free, copper is reactive and toxic. In water, copper is quickly bound to organic matter in the water and in the substrate, e.g. B. of humic acids.
In alkaline water, copper ions bind to calcium carbonate, reducing the amount of free copper ions in the water. However, carbonates are part of the so-called pH buffer. When the pH drops later, the toxic copper ions are released again.
The medicinally effective amount of copper at higher pH can thus become a lethal dose at lower pH.
At very low pH values, the water has little buffering and copper can become very toxic. At pH levels below 6, even previously absorbed copper can become soluble and toxic again. Even copper that was still bound in the aquarium after treatment a long time ago can become harmful again.
copper in tap water
High levels of copper in tap water most often result from using water from copper pipes or warm or hot water from water heaters. The heat exchangers of water heaters are also made of copper.
Warm water from water heaters should therefore never be used in the aquarium. Water from copper pipes can be allowed to drain for a long period of time until all of the copper residues dissolved from the pipe have drained. The water must drain for at least two minutes.
With an osmosis system or an ion exchanger, copper can be removed from the water before the copper even gets into the aquarium.
If the amount of copper in the aquarium water is not yet harmful, the amount of copper can be reduced by filtering through peat.
Harmful amounts of copper should first be bound with a water conditioner, since the copper can only be removed slowly. The chelators contained in the water conditioner bind the copper and initially render it harmless. With numerous water changes, the chelated copper is then removed from the aquarium.
Because copper likes to settle in the substrate, bottom-dwelling fish or fish that eat a lot from the bottom should be moved to another aquarium.
Fresh activated carbon can remove some of the free copper. Activated carbon used for this must then be removed. However, activated carbon does not remove all of the copper. Copper bound to humic substances remains e.g. B. in the aquarium and can be released later.