Copper (Cu)
Copper is extremely toxic to invertebrates and corals even at very low concentrations. It serves only as a drug treatment for some fish diseases.
Detailed explanation
Copper is the number one enemy of marine invertebrates. Concentrations of 0.01 ppm are enough to kill shrimp and coral. For this reason, copper drugs are never used in an aquarium with invertebrates.
Inadvertent sources of copper are insidious: household copper pipes (the first litres of tap water in the morning have high concentrations), pumps with copper or bronze components, some cheap sea salts, contaminated rocks, heaters with copper coils.
Copper is used as a pharmacological treatment for marine ich (Cryptocaryon irritans) and velvet (Amyloodinium). But only in quarantine aquariums without invertebrates. The therapeutic dose is 0.15-0.25 ppm maintained for 30 days. Even a day of interruption can make the treatment fail because the parasites have resistant phases in the life cycle.
An aquarium treated with copper will never have to host invertebrates again. Copper is absorbed into silicone, rocks and substrate and slowly released over months.
ICP analysis detects copper accurately. If you find copper in your reef tank and have never added it, look for the source (pipes, pumps, rocks).
Reference values by aquarium type
| Aquarium type | Recommended range |
|---|---|
| Marine (reef) | 0 ppmMust be zero in a reef. Any trace is dangerous for invertebrates |
| Tropical freshwater | 0 ppmShrimp are very sensitive |
How it is measured
Drop test (Salifert, Seachem MultiTest) for quarantine aquariums. ICP analysis to detect contamination at low concentrations.
What happens when it is too low
No problem. Must be zero.
What happens when it is too high
Rapid death of invertebrates. Melting corals. Shrimp and crabs dead within hours.
Coralia Lab monitors this parameter with AI diagnostics. Tank Score alerts you when a value moves outside the recommended range for your aquarium.
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