What copper treats
Copper is a long-established treatment for two common marine parasites: marine ich (Cryptocaryon irritans) and marine velvet (Amyloodinium ocellatum). It works against the free-swimming stage of these parasites. Some hobbyists report that it suppresses symptoms of other diseases, such as Brooklynella or Uronema, but it is not considered a reliable cure for them. Learn how to tell these problems apart before treating; our article on ick on saltwater fish covers symptoms in more detail.
Is copper harmful to fish?
Yes, it can be. Copper is a toxic substance, and the aim is to keep the level high enough to affect the parasite but low enough that the fish tolerates it. Some species are more sensitive than others, and fish that are already weak may have more trouble. Stress, unstable levels or overdosing can all harm the fish. If you have a delicate species, consult the medication’s label, an experienced hobbyist or an aquatic veterinarian before starting.
Never use copper in a reef tank
Copper is toxic to corals, anemones, snails, shrimp and other invertebrates, and it can be absorbed by rock, sand and equipment, then slowly released later. For that reason it should be used only in a bare hospital tank without live rock, sand or invertebrates, never in a display reef tank. Use dedicated equipment and tubing for the hospital tank when possible. Our guide to saltwater fish care explains how to set up a simple quarantine tank.
Copper products and therapeutic levels
The right level depends on the product. Different brands use different forms of copper, and the target concentration, called the therapeutic level, is not the same across them. Hobbyist sources commonly describe ranges such as:
- Chelated products like Cupramine, with a target of about 0.5 ppm
- Ionic copper sulfate products, often with a lower target of around 0.2 ppm
- Other chelated products such as Copper Power or Coppersafe, with higher targets in the range of about 1.5 to 2.5 ppm depending on the product and source
Because the numbers differ by brand and sources do not always agree, treat these as examples only. Always follow the instructions on the exact product you buy, and use the test kit that the manufacturer says is compatible with it.
Testing copper accurately
Keeping copper at the therapeutic level is the most important part of treatment. Too low and the parasite may survive, and too high and the fish may suffer. Test daily, and adjust only as the product directions allow. Many hobbyists find that inexpensive color-matching kits are hard to read, and prefer a digital colorimeter built for copper. Make sure that the checker or test kit you choose can read the type of copper in your medication, as some kits do not detect all forms.
How long to treat
Treatment length depends on the method. Commonly cited approaches are:
- Two-tank method: treat at the therapeutic level for about 14 days, then move the fish to a separate, clean observation tank. The 14 days start only once the level has reached the therapeutic range and stays there.
- Single-tank method: keep the level in range for a longer period, often about 30 days, because the parasite’s life cycle can be prolonged and there is no second tank to move to.
These are widely discussed in the hobby, but they are not the only protocols. Product labels may recommend different lengths, so check yours. If copper drops out of range partway through, many guides recommend restarting the count.
How much copper per gallon?
There is no one answer. The dose depends on the product’s concentration, the tank volume and the target level for that product, so a per-gallon figure copied from a forum may be wrong for your medication. Follow the label for the amount to add, then confirm the result with a suitable test kit and adjust cautiously. Avoid guessing, because overdosing can kill fish.
How long until ich falls off in copper?
Spots may disappear within days, but that does not mean the parasite is gone. Treatment has to continue long enough to affect parasites that were encysted when you started and that release free-swimming young later. This is why guides emphasize completing the full course even after the fish look clean.
After treatment
- Watch the fish for a few weeks in a copper-free observation setup.
- Keep water quality high during treatment, because fish are stressed and ammonia can rise.
- Keep the display tank fish-free for an adequate period if it has been exposed to the parasite. See ick on saltwater fish for more on fallow periods.
- Remove copper from the hospital tank water and equipment carefully before reusing it, for example with activated carbon or a copper-removing resin, as instructed by the product.
- Think about prevention next time by quarantining new additions. For choosing peaceful tank mates afterward, see compatible reef fish.