Preparation

Once ick has been discovered in a tank, the first task is to prepare the tank for treatment. If any filters contain activated carbon for chemical filtration, remove it. The activated carbon will remove the medication from the water. UV sterilisers and protein skimmers should also be switched off in order for the treatment to work effectively.

The water in most goldfish tanks is at room temperature (roughly 18 Celsius/65 Fahrenheit), so there is no general requirement for a thermostat. However, using one to gradually increase the water temperature by half a degree celsius every day will reduce the length of treatment. This is because the ick is only treatable during the theront (free swimming) phase of the life cycle. Due to the fact that an increase in temperature speeds up the life cycle, the theront phase will arrive quicker at higher temperatures.

If possible, bring the water temperature up to 26 Celsius (80 Fahrenheit) and the treatment will be over in 10 days. Keeping the temperature low will mean the treatment will need to continue for 6 weeks. One word of caution though – when the ick life cycle takes a week, a new dose of parasitic infection comes round every week. If anything is wrong with the treatment program it could result in heavy infestation, and goldfish dying off quickly.

Finally remove any snails, and check if any aquarium plants present are sensitive to the recommended treatement – malachite green.

Treatment

Malachite green is a widely available chemical treatment for ick. Other chemicals that can be used are formalin, copper, quinine hydrochloride, methylene blue and sodium chloride. However, non of these are any better than malachite green, which has the advantage of been successfully used to treat ick for many years.

Follow the dosing instructions on the label to the letter, taking care to avoid eye and skin contact. Malachite green leaves a stain on almost everything it touches.

At the ideal temperature, continue the treatment for 10 days. This will ensure that the theront phase of the ick life cycle will have been exposed to the malachite green. During the trophozoite and tomont phases, the chemical will have no effect on the parasites. In both cases they are enclosed in protective cysts that are impervious to any known treatment.

Although the life cycle only takes a week at this temperature, the treatment should go on for 10 days in order to make sure that all traces of ick have been removed.

It is worth noting that the treatment for ick treats the water. When treating the vast majority of goldfish diseases it is the goldfish itself that is treated. However ick can only be killed when it is vulnerable, and that is when it is out in the water.

Prevention

As is the case with every goldfish illness, prevention is better than cure. Make sure the water is tested regularly, feed the fish a balanced diet, change the water regularly and don’t put too many goldfish in the tank. These measures should be par for the course in every single goldfish tank and pond.

Also, never buy aquarium plants that are in a tank with fish in the pet shop. Tomonts stick to plants, and a single one provides an easy passage for up to 1000 individual parasites.

When bringing a new fish home for the tank, put it in a quarantine tank for whatever length of time the ick life cycle takes at the water temperature of the quarantine tank.

Ick is common and deadly, but following the advice above will save goldfish from the disease, and bring them back to rude health as quickly as possible.

Trophozoite

This is the phase of the ick life cycle when the parasite is living in the skin of the goldfish. It is a spherical shape with a cup shaped mouth at one end. The mouth contains very fine hair-like structures called cilia, that beat rhythmically and continuously inwards. These cilia scrape tissue from the body of the goldfish and pass it into the mouth.

Goldfish produce a natural reaction to the trophozoite – they surround it with a hard casing that forms a cyst. It is these cysts that are the most noticeable symptom of ick – the appearance of being sprinkled with salt.

Depending on the temperature of the water, the trophozoite grows to between 0.1mm and 1mm wide, and after about a week it falls off the goldfish. It swims in downward spirals to the bottom of the aquarium, or sticks to a plant or ornament.

Tomont

Once the released trophozoite has settled, it absorbs its own mouth and secretes a gel around itself, becoming known as a tomont (or trophont). It then starts to replicate inside the gel casing. The cells produced by the first few divisions form an internal wall on the gel casing, but the rest of them develop into parasites.

The number of cells produced in the tomont can reach 1000, and will usually be at least 600. This phase of the ick life cycle will be complete in anything between 8 hours and several weeks, depending on water temperature.

When complete, the tomont bursts and releases the individual cells called theronts. These look for goldfish to burrow into.

Theront

Theronts (also known as tomites) are microscopically small and oval in shape. They are good swimmers and move about the aquarium until they find a goldfish to latch on to and burrow into.

They swim with cilia and are thought to burrow into goldfish skin using these cilia, and possibly a combination of mechanical and chemical attacks on the integrity of the goldfish skin using a pointed structure and a capsule of chemicals found at the front of the parasite. It is after they burrow into the skin that they grow their mouths.

Theronts can survive for a maximum of 4 days without finding a goldfish to feed on, and in most cases they will die after 2 days.

How long does it all take?

It all depends on water temperature. The warmer the water, the quicker the ick life cycle is complete. At a temperature of about 20 Celsius (70 Fahrenheit) the cycle would take up to 4 weeks. Raising the water temperature to 26 Celsius (80 Fahrenheit) would see the process complete in about a week.

As the optimum water temperature for goldfish is at the lower end of the scale, the ick life cycle will take much longer in a goldfish aquarium or pond.