Copper 101


Reefing newb
Thank goodness for copper! Thank goodness that the most troublesome and devastating parasites :evil: to our ornamental marine fishes are killed by the use of copper. But it can't be used casually or as a kind of 'answer-to-all' problems. It's use by aquarists comes with the need for responsibility and attention. After all, copper is a poison to our fish and in the effort to kill off the parasites, we can kill off our fishes. What's worse even, is the abuse of copper can shorten the lives of our captive fishes.

Copper is nowadays used almost exclusively to kill Marine Ich (Cryptocaryon irritans) and Marine Velvet (Amyloodinium ocellatum) infections on our ornamental marine fishes. (I'll use MI and MV to refer to these parasites and the conditions they cause).

I'm sure what is written in this post is familiar to some or all of you, in part or in whole, but it should be clearly stated in one place.


It's not much of a secret. The ornamental marine fish hobby owes what we know about MI and MV to the studies, research and monies thrown at controlling these parasites, by the aquaculture industry. 70 years ago the aquaculture industry was plagued by these problematic parasites and then it was found that copper could kill both these parasites at a concentration that wouldn't kill many of the food fishes.

One issue that the aquaculturists faced with the copper treatment is how much free copper ions love to complex with carbonates and how lethal it was to the fish. For the aquarist, this means that adding copper in its ionic form to saltwater will cause the copper to attach to substrates, rocks, other carbonate-based things, and even glass! Treatment with copper requires diligence and control.


Copper Salt (Cu2+, cationic or ionic copper)
At first the basic copper medication was a water mixture of a copper salt (e.g., copper sulfate). The copper concentration in this form is hard to control in saltwater. Copper in this form will easily complex with carbonates -- even carbonates that were in the salt water making up the alkalinity! The copper would precipitate out of its dissolved state and no longer be available to do the job of killing off the parasites. These medications I remember well. When added to the aquarium water, there would be a 'cloud' of bluish-white haze in the aquarium water. This was some of the copper coming out of solution.

Controlling the copper concentration in this form was a problem for the aquaculture industry, and a nightmare for the hobbyist. The aquaculture industry had neither the time or the money to keep testing their water to hold the copper in the 'effective range' to kill the MI and MV, yet not kill their stock. This copper was so 'effective' at killing (even fish) that some fish just couldn't even live in the concentration it took to kill the MI and MV. By this, I mean to make clear that the copper in this form is very lethal even to the fish it is supposed to treat. This copper medication isn't even considered a choice by today's standards.

Then the use of copper 'crashed.' It was no longer allowed for use by the aquaculture industry. Food fishes cannot be treated (in the USA) using copper medications. The ornamental trade picks up the challenge.

Chelated Copper
The next major development in the medication, was to 'protect' the copper from complexing and coming out of solution so readily with the carbonates in the water. Thus came the 'chelated copper' medications. (Chelated is pronounced KEY'lated). The copper was more reliable for staying in solution. What was done was to shield the copper ion with a weak, very large molecule (e.g., Ethylenediametetraacetic Acid, a.k.a EDTA) The copper ion still complexed with carbonates and the copper still precipitated out of solution, but not as much. The chelated copper was more stable compared to the plain copper salt medications. More fish now could be treated with this form of copper. But the most sensitive of fishes (e.g., dwarf angelfishes, some large angelfishes, some tangs, and scaleless fishes (sharks, rays, eels, etc.)) could not be treated with this form of copper.

Complexed Copper
The serious breakthrough came when the copper, instead of protected by a weak complex in the chelated form, could be chemically bonded to a protein molecule. In this case, the copper is still lethal to the MI and MV, but it keeps an arm's length away from affecting the fish. It resists complexing with carbonates making the concentration much easier to control and to get to remain steady. This copper form could now be used on any ornamental fish, and scaleless fish. This complexed copper is safe and yet effective at killing off MI and MV.


When copper ions get into our aquarium water, they will complex with several other salt water ingredients and some of the things we put in our aquariums. Copper ions, as noted above, are very fond of forming complexes with carbonates. When they do, this complex is not very soluble at the pH of our aquariums and it will precipitate, or come out of solution.

Copper ions will do the same with rocks and substrates that contain any form of carbonate materials. This is one reason why it is best to use copper medications in a bare-bottom hospital tank without live rock, dead rock, and carbonate based decorations.

The precipitated copper-carbonate will redissolve if the pH of the aquarium water goes down. This has the effect of suddenly increasing the amount of copper in the tank water. So, the aquarist thinks they are in control of the copper concentration only to find that there is a surge of copper when the pH drops. In addition to maintaining the effective copper concentration, attention has to be given to the holding the pH of the water steady. By the way, this surge in copper, no matter how short of time it is, is enough to permanently injure, poison, or kill the fish being treated.

Another thing has to be made clear about copper as a medication. It is a poison as has been stated previously. Copper can and does cause stress in the fish and thus, does some harm to all fishes at detectable (by test kits) concentrations.

Copper medications can harm the fish without the aquarist even realizing. In 'effective concentrations' that kill the disease organism, copper stresses the fish and in effect is slowly killing it. Furthermore, (even in low concentrations) copper can stress the fish and weaken it, allowing all sorts of other conditions to affect the fish. I have to be the 'adult' here! Copper is not a toy!

If you decide to use a copper treatment the fish might stop eating. Copper is a stress to the fish and some fish respond by not eating, acting in a peculiar manner, or becoming afraid of its own shadow/reflection.

Lastly, if you choose to use a copper medication/treatment process you should know that the equipment will need special cleaning after the treatment if inverts and/or corals will be kept in the QT.


Not only does each type of medication have its own effective concentration, but so does each manufacturer's product. We can't make any general statement about how long to treat or how much copper needs to be in solution for it to do its job. Simply put, only the medication manufacturer knows what they put in the product and thus how to properly use the product.

In short, follow the manufacturer's treatment recommendations very closely.

But no matter what the copper medication manufacturer recommends, the aquarist needs to know what copper concentration range should be used in the treatment. Only the manufacturer knows this.

And since only the manufacturer knows how to properly test for the copper in their medication formula, the aquarist needs to know what copper test kit to use in measuring the copper concentration.

Armed with:
the medication;
having the right test kit for copper recommended by the copper medication manufacturer;
knowing the copper concentration range the manufacturer recommends; and
a bare hospital/quarantine tank

the aquarist is ready to perform a copper treatment. Some manufacturers try to make it easy by just stating in their instructions to add a quantity of their medication per gallon (or per some other volume) to your water, but in the marine aquarium world, everyone's tank is different. One addition doesn't work the same in all hospital tank systems. You need the control of measuring, knowing the target copper concentration range, and holding the copper in that range.


The copper concentration has to be kept in exactly the correct range for it to work properly. As stated above, only the medication manufacturer knows what range is right for their medication. So I can't and no one can say a general/proper range.

In the case of using Cupramine, the manufacturer, Seachem recommends that at first the amount added is half the final dose. Then later the rest is added to bring the concentration to 0.5ppm. FOLLOW THESE DIRECTIONS. Adding half dose allows the fish and biological filter to have a short time to acclimate to the addition of copper. After the second dose totally mixes in, then start the testing for copper.

However, if the copper concentration drops below the concentration needed to kill the MI and/or MV, the treatment will have no effect.

Likewise, if the copper concentration exceeds (goes above) the high-end concentration, the fish could suffer, become poisoned, and/or die. This is a situation where clearly, more is NOT better.

If using Cupramine, use either the Seachem Copper Test Kit or the Salifert Copper Test Kit to measure the copper concentration of Cupramine. Many hobbyists complain the Seachem Copper Test Kit is too hard to use. Fortunately the Salifert Kit isn't.

For the above reasons, it is important that the aquarist knows how much of the copper is in the water and doing its job. AND must keep it in that range. Any slip means the treatment time has been wasted (and possibly will kill the fish if overdosed).


With the current advances and availability of good copper test kits like we've never had before, I strongly recommend the use of Cupramine as a copper medication. It is in that third category of being a complexed copper and very safe for use on all ornamental fishes including sharks and rays.

The proper copper test kits to use for Cupramine medication is either the Salifert Copper Test Kit or the Seachem Copper Test Kit. I hear many complaints about how hard it is to read the Seachem Test kit. And the rumors are true that in late 2005 and early 2006 there were Seachem Copper Test Kits on the market that expired before their time and gave erroneous readings. But. . .who's perfect?

The Salifert Copper Test Kit is quicker and easier to use. However, it goes from 0.5 ppm copper indicator straight to 1.0 ppm copper (with no in between comparison color/shading), then the next color is greater than 2. ppm. Cupramine is best used between 0.3 and 0.8 ppm. So this scale doesn't give you much information. You can use Cupramine very effectively at 0.5, though 0.6 ppm is preferred for the 'tougher fishes.' For sharks, angelfishes, etc. 0.3 to 0.5 ppm would be preferred, in my opinion. There is a way around this test kit situation.

If you prepare freshly made up saltwater (like you were doing a water change) and test that for copper, you can then use that to dilute your tank sample water for the Salifert Copper test, remembering to account for any copper reading of the freshly prepared water. Thus, you can get the relative accuracy you need from the Salifert Copper Test Kit reference colors. (Just remember to calculate the copper concentration reading by the dilution factor).

NOTE: In the case of using Cupramine, the manufacturer Seachem recommends that at first the amount added is half the final dose. Then later the rest is added to bring the concentration to 0.5ppm. FOLLOW THESE DIRECTIONS. Adding half dose allows the fish and biological filter a little time to acclimate to the addition of copper. After the second dose totally mixes in, then start the testing for copper, ammonia, and nitrites.

One advantage of Cupramine is that it is a 14-day treatment AFTER the copper concentration is up into the range (after the second dose). Other medication manufacturers claim their treatment takes longer or shorter, but the 14-day treatment makes sense when you review the life cycle of MI and MV.


Treating with copper cannot be done with many other treatments and medications.

Copper should not be used with any kind of sulfa-based antibiotic.
Never perform a copper treatment in a hyposaline solution. The copper becomes lethal to marine fishes in such a low salt concentration.
Hyposalinity only cures one parasite -- Marine Ich (Cryptocaryon irritans). Copper kills Marine Ich also, so there is no purpose in doing both the copper AND a hyposalinity treatment at the same time (see above red).

What can go wrong?

Treating with copper can cause or lead to any or all of the following:
1) The fish stops eating from the stress of the copper;
2) The biological filter stops or slows (some bacteria go into a stasis mode when confronted with the copper ion). The aquarist has to monitor ammonia, pH and nitrites daily during the copper treatment. Such affected bacteria will resume their function, but it may take days or weeks;
3) Water parameters change. Diligently monitor copper, pH, ammonia, and nitrites;
4) Excess stress on fish. Lower lighting and perform treatment where few humans go, to avoid additional stresses;
5) Copper contamination of equipment. Copper is not easily removed to low enough levels after its use. If the QT and equipment will only be used for fish, then a thorough soap cleaning should be good enough. If the QT and equipment will be used for inverts and/or corals, a special cleaning will be necessary; and
6) I've successfully used Cupramine two years after it has been opened, past its shelf life. However, it is prudent to use Cupramine that has been on your LFS's shelf less than a year.