Treating white spot disease

By Frank Greco, AnimalForum.com staff
Copyright 1997 by Frank M. Greco

The common name for this disease is white spot disease or Ich. The scientific name is Ichthyophthirius multifilis, and the organism is ciliated protozoan.

Symptoms: Obvious white spots on the body and/or fins of the infested fish. Spots may resemble grains of salt. The spots (actually, cysts) may be up to 1 mm in diameter, or may join together to form irregular patches. Heavily infested fishes may scratch themselves on the bottom or tank decor, and rapid respiration may be evident.

Life cycle: Adult parasites, which feed upon the tissue of the fish, fall into the substrate layer. There, it divides many times, producing several hundred tomites which are the infective stage. The tomites swim into the water column in search of a host and, failing to find one, die in a short time. If they do find a host, the tomites attach and encyst. The life cycle is temperature dependent, and can occur in three to four days at 70 degrees F and up to five weeks at 50 degrees F. At lower temps, the parasite will remain dormant.

Treatment: As long as the parasite is encysted on the fish, it is immune to treatment. However, at the first notice of these cysts, treatment should be started. Malachite green is generally safe to use for most freshwater species. I know some of you must be shaking your heads, saying that malachite green will kill some freshwater species. Nonsense! When dosed correctly, malachite green is safe for even the most so-called sensitive species.

The correct dose is 0.05 ppm malachite green for three treatments, one every other day. At this level, your fish should not experience malachite sensitivity. Of course, dosing at 0.05 ppm means doing more than adding one drop per gallon. To figure out the correct amount of liquid to add, you take the concentration of malachite green listed on the bottle (in percent), and convert it to milligrams per milliliters (percent= 1 gram/100 milliliters of water). Divide the milligrams per milliliters by the final concentration. This will give you the results in milliliters/liters. To convert to gallons, divide the number of milliliters by 3.8.

For example, we have a 10 gallon tank, want a final concentration of 0.05 ppm (or 0.05 mg/l. It's interchangeable for our purposes), and we are using a 0.75% malachite green solution. So...0.75% = 7.5 mg/milliliter. 7.5 mg/ml divided by 0.05 ppm (or mg/l) = 1 ml per 40 gallons. Since 1 milliliter is about 16 drops, we will need 1/4 of that, or 4 drops per 10 gallons of a 0.75% malachite green solution.

Now for the kicker: Most medications advise one drop per gallon. This works out to 2.5 times the amount actually needed. No wonder some hobbyists lose fish when using malachite green: they have severely overdosed.

Another popular treatment is the use of aquarium or marine salt. Bringing the level to 5 ppt will generally eradicate the parasite. Some catfishes may be sensitive to this salt level, and so if you do have catfish in your tank, go no higher than 2 ppt. In either case, use whatever level you choose as an indefinite bath for 14 days.

Also, it has been noted that raising the temperature will also "cure" the condition, but I would advise against this because:

• An increased temperature also increases the metabolism of the fish, which causes it to require more oxygen. However, there is less oxygen in the water the higher you go with the temperature. This produces more of a stress on the fish, and may delay a full recovery.

• The use of temperature alone is not necessarily a cure. While it may accellerate the life cyclacceleratee, it does not guarantee a 100% kill.