Copper Toxicity for invertebrates and fish in a planted aquarium

Quite often one of the first questions a newcomer to planted tanks will ask is – “Does this contain copper?” when referring to one plant food or another.
More often than not this is because of the “Copper Myth” – Much like the Nitrate/Phosphate/Algae myths the copper myth is enduring…..
The Myth – Copper kills inverts
The Fact – Copper treatments (can) kill inverts………plant foods are not copper treatments.
Here’s a fun fact – Haemoglobin that carries oxygen to our cells requires Iron…so we bleed red. Haemocyanins the invert equivalent you might say uses Copper in the same way, so they bleed blue.

Lets take a look at the figures – The Median Lethal dose or LD50 is the level required to kill half of the population of a given group. Below is a table showing the LD50 for various species – If you have a value for your copper level either from a test kit or the output from one of our calculators, you can input the value at the bottom of the table and see how you fair. Just hit “Update” after.

Source –
PAN Pesticides Database – Fish
PAN Pesticides Database – Crustaceans

This information is for reference only – quality studies are few and far between – your mileage may vary.
Based on the original research of Wet – Petalphile.

  • Troy Young
    Posted at 12:07h, 27 July Reply

    I would like to see this expanded to include comments regarding the effect of strong / weak chelating agents, and the presence of SO4, on the toxicity of copper in the aquarium.

  • Marcel G
    Posted at 15:22h, 15 February Reply

    I am afraid that your underlying premise about LC50 is wrong. Although LD50 is the level required to kill half of the population of a given group, this does not mean that lower concentration can’t be toxic or detrimental to that population. In fact, the “safe level” (reffered to as PNEC = predicted no-effect concentration) is usually thousandth of LC50 (PNEC = 1/1000 of LC50). So if average LC50 for Caridina sp. is 0.072 ppm, then the “safe level” is considered to be 0.072/1000 = 0.000072 ppm = 0.072 ppb !!! Anything above that level can have negative effect on that species. So based on these facts, even the Guppies can be negatively affected by as low as 0.007+ ppm Cu. So your “Copper Myth” does not seem to be such a myth as you may have thought originaly.

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