Fish Health, Saltwater

Treating Saltwater “Ich”

Saltwater ich is a disease caused by tiny parasites of either Cryptocaryon or Oodinium. These parasites imbed themselves in the fish’s skin and gills, causing great irritation. Initial symptoms usually include loss of appetite, rapid breathing and scratching. The parasites feed and grow for a few days, then drop off the fish in preparation for reproducing. They lie on the tank bottom in an encysted state for several days or weeks and mature. Each cyst then ruptures, releasing dozens to hundreds of new parasites to begin the cycle once again. In nature or in very uncrowded aquariums, very few of these parasites are successful in finding a host, and their population is kept in check. In a more typical aquarium situation, however, the number of parasites multiplies tenfold or more with each cycle, and the fish are soon overcome.


Saltwater ich parasites are commonly found in nature, and we can safely assume that many normal, healthy fish are carrying a few of these parasites when collected. Since no treatment has been found that can kill ich while embedded in the fish, we must wait for all of the parasites to fall off on their own before we can consider the fish to be ich-free. In the meantime, of course, effective medication must be used to prevent re-infection. Ideally, each hobbyist should have a medicated quarantine tank, to isolate and treat each new specimen for at least two weeks before addition to the main aquarium. Another option is to purchase only specimens which have been kept in properly medicated tanks at least two weeks at your dealer (we medicate all our fish-only tanks full time and we date our fish labels to help you with this). Saltwater invertebrates are suspected of being carriers of ich, and since most effective ich treatments also kill invertebrates (their cell structures are quite similar), they cannot be guaranteed ich-free when purchased.


Saltwater fish have a number of natural defenses against ich, and if the fish are healthy enough and the outbreak mild enough, sometimes the fish may cure themselves, just as they would in nature. We can assist them to some degree by maintaining good water quality and providing a nourishing diet. Raising the water temperature shortens the disease cycle and may add vigor to the fish’s defense system. Lowering the salinity to about 1.015 seems to inhibit the breeding cycle of the parasites. Giving the fish a two minute freshwater dip may eradicate parasites from the outer layers of skin and gills. Keeping only a few fish in a large aquarium (as in the currently popular “reef” type tanks) can make it harder for each parasite to be successful in finding a host, and the disease may die out.

It is very important, however, not to mistake a temporary reprieve for a complete cure. Quite often, ich symptoms subside for a week or two, only to return a hundred fold with the next wave of parasitic swarmers. In another common situation, the ich and fish reach a sort of “stand-off”, where neither the fish nor the parasites get the upper hand. The fishes natural defenses keep the disease under control and the symptoms disappear, but there are still plenty of parasites in the aquarium. Any new fish added are quickly overwhelmed by parasites and die in a few days.


For many aquarists, treating for ich is inevitable, and there are a great number of commercial “remedies” on the market. Unfortunately, we have found many of these to be ineffective and most to have dangerous side effects in spite of claims on the label. Over the years we have tried most of these (including malachite green, formalin, quinine and methanidizole), always hoping to find a treatment a little better or a little easier than what we are using. While our current system has some shortcomings, we have found it to be very effective if used correctly, and it has a fairly wide margin of safety. We use Cupramine® copper treatment and maintain a concentration of .30 ppm for at least three weeks. Some stubborn Cryptocaryon infections require increasing the level to .35 ppm. Most fish can survive levels of up to .8 ppm for short periods of time. Like other copper treatments, Cupramine® kills invertebrates. Since copper is absorbed by saltwater gravels and decorative corals, a reliable, readable copper test kit is necessary. We have found the Hanna Handheld Colorimeter for Copper (High Range) to be a very reliable and affordable method for checking copper levels in aquaria. We have them available in store to check customer’s copper levels, and sell the meter and reagents for home use.

Medicating with Cupramine® Copper

  • Use copper to treat protozoan infections.
  • Remove all invertebrates (crabs, shrimp, anemones, etc.) before medicating.
  • Remove chemical filter media (carbon, Chemipure®, Poly Filter®, etc.) during treatment.
  • Build up slowly. If tank has never had copper before, use no more than one drop per two gallons each day for first two weeks. Thereafter, one drop per gallon is a full dose. Discontinue treatment temporarily if ammonia or nitrite levels rise.
  • Use test kit to determine copper level before each treatment. If level is zero, you may add a full dose of copper (unless still in “build up slowly” stage). As level approaches .30 ppm, use a proportional amount of copper (for example; if test shows .15 ppm, use 1/2 drop per gallon of Cupramine®).









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