Symptoms: Small white spots on a fish’s skin, looking like large grains of salt were sprinkled on the fish. Fish will usually “flash,” swimming very quickly and scraping itself against gravel or tank ornaments.
Vulnerable species: Scaleless catfish and mollies in the absence of salt.
Cause: A three-stage protozoan parasite:
The trophozite form of ich, embedded in the fish’s skin, causing the white cyst. It is feeding from the surrounding flesh, preparing for the reproductive phase:
The trophozite has now matured into a trophont. It falls off the fish’s skin to the bottom of the aquarium and beings to create hundreds of new parasites:
Tomites swimming freely, seeking a host. The trophont has burst, releasing hundreds of these tomites, which then restart the cycle.
Treatment: Treatment is difficult because of the nature of the 3 life stages. During the trophozite and trophont stage, the fish’s slime coat and the parasites’ own mucous layer protect the parasites, respectively. The only treatable stage is the tomite. Because the life cycle takes about 2 weeks, if you start medicating right when a new cyst forms and stop before the resulting trophont bursts, you will have a whole new infestation. It is therefore recommended that you treat for 4 weeks, or 2 full life cycles. Increasing temperature speeds this cycle, potentially shortening treatment time. Copper sulfate can cure and prevent the outbreaks at 0.15-0.20 ppm. Other treatments are malachite green, formalin, and methylene blue. Treatment with malachite green and methylene blue should be used with caution, for catfishes are especially sensitive to these industrial dyes. They can be found in special solutions specifically for ich treatment at most fish stores. Apply as directed on the bottle, but disregard the treatment period: it is usually well short of 2 full ich lifecycles. Garlic is also believed to be an effective cure and preventive measure. Note that salt has little effect on the parasite, but it mildly increases a fish’s skin’s resistance to the parasite. (Increasing the slime coat)
Pathology: Widely believed to be present in nearly all aquariums. There is a freshwater and saltwater version. Usually caused by introduction of a new fish, which is either infected or has been so weakened by transport and location shock that it becomes infected. Because of this, quarantine of all new fish is recommended to watch for a developing case. In all any case, a new fish showing signs of ich should be immediately quarantined. If a few fish of a community develop ich, quarantine is not practical as the parasite is present in the whole tank. Vacuuming the gravel can remove some of the reproductive parasites, which is of some small help to treatment efforts.
Note: Malachite green is deactivated by sunlight. Avoid sun exposure to the tank during treatment. Store malachite green in a dark area. Do not refrigerate.
© Eric Smith
Malachite green is a suspected carcinogen. Gloves should always be worn when coming into contact with the chemical AND water being treated by it. It irritates fish’s lungs and reduces dissolved oxygen, thereby increasing risk of suffocation. Be very careful and conservative during dosing, and remember that decorations and gravel reduce a tank’s actual capacity by 5-10%. An average 20 gallon tank should therefore be treated for 18 gallons, only 9 if loaches and catfish are present. BE CAREFUL.