Ich (Ichthyophthirius multifiliis) is a protozoan parasite that is one of the most
common afflictions of aquarium fish. It is highly contagious and will be deadly if
not treated quickly and eradicated completely. In order to understand how to treat
ich, it is first necessary to understand the life cycle of the parasite.
- Trophont Phase: This is the phase when you discover your fish have ich. The parasite burrows
through the slime layer and becomes encased in a hard shell which is often called a "cyst." It is
these cysts that have the distinctive "grains of salt" appearance. The parasite at this stage is
immune to medication, being protected by the skin of the fish and the hard shell of the cyst.
- Tomont Phase: When the parasite matures it breaks out of the skin, still encased, and falls away
leaving a tiny open wound in the skin of the fish. The cyst falls to the bottom of the tank or into
the cracks and crevices of an object such as a rock or plant. Inside its casing the tomont divides.
At this stage, the parasite is immune to treatment.
- Theront Phase: When the tomont ruptures it bursts open to release hundreds of theronts into the water.
This is the phase of the Ich life cycle when the parasite is vulnerable to medication. Theronts
have a life span of approximately two days and will die if they have not successfully located a
host fish.
Understanding the life cycle of the ich parasite is crucial to treatment. As you can see,
there is only a very short time that the parasite is vulnerable to treatment. Medications
which claim to cure ich in 2 days are optimistic, at best. The duration of this cycle is
dependent on temperature. At 70 degrees Fahrenheit, the cycle takes 18 days; at 80degrees, 10 days;
at 85 degrees, 6 days.
Treatments
- Copper (CopperSafe, Aquarisol): Copper is safe for all fish, even scaleless and very young fish.
It is hard on plants and lethal to invertebrates such as snails and shrimp, which cannot be added
back to the tank for some time.
- Analine Green (Maracide): Although related chemically related to Malachite Green, it is safe
for scaleless fish and, importantly, for humans. Easier on plants and invertibrates than copper.
- Formalin (Rid-Ich, Formalite, Quick-Cure): Formalin is a mix of 37% Formaldehyde, 6 to 15% Methanol,
and water. Do not use with scaleless fish such as loaches. Be sure to ventilate the area, as formaline
fumes can be toxic.
- Malachite Green (Quick Cure, Rid Ich, Super Ich Cure): Although very efficacious, Malachite
Green is toxic to scaleless fish, NOTE: Malachite Green is known to cause cancer, mutations,
and harm to fetuses. It should never be used where a pregnant woman is present.
- Quinine (Clout, Quinsulex): Extremely strong medication which should be considered
only as a last resort.
- Salt and Heat: Salt at the rate of 2-3 teaspoons per gallon in temperatures over 85 degrees.
It is critical that you confirm that every species of fish in your tank will tolerate treatment
with heat and salt. In general, heat and salt should not be used to treat planted tanks,
though some species of plants may survive it. It has been reported that Java Fern and Java
Moss are tolerant of salt treatment. Salt should be added to the tank slowly and should be
pre-dissolved in a large volume of water, as salt can burn fishes' skin.
Treatment should continue for five days after the last spot disappears,
normally 14-21 days.
Undoubtedly the best procedure for avoiding ich in your tanks is quarantine. Two weeks with medication
or four weeks without medication (assuming no symptoms are present) will prevent the ich parasite and
other possible illnesses from being introduced into your tank.
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