Fish White Spot Disease – Ichthyophthiriasis
- Primary symptoms: Fish appears to be dusted with small white dots (about 1mm, the size of grains of fine salt or sugar). These are cysts in which the parasites develop: the parasites will leave their adult host, fall to the ground and then find other hosts (otherwise they die quickly). Be careful not to confuse the symptoms of white spot disease with those of velvet disease: the spots of velvet disease are absolutely tiny (about ten times smaller) and closely spaced, giving the skin the appearance of velvet, their color ranging from yellowish to greenish depending on the lighting.
- Secondary symptoms: Rapid or labored breathing in the event of a heavy infestation (damage to the gills). The fish may stay just below the surface, gasping at the surface of the water. Sometimes, presence of a white, milky film on the fish body (production of excess mucus in response to the threat of parasites). Darting and scratching: the fish may rub against the stones or tank decoration. The affected fish may isolate itself from the rest of the group and display clamped fins.
- Direct causes: Ichthyophthiriasis (protozoan).
- Contributing factors: Sudden temperature changes (e.g. water changes with water that is much too cold), stress factors (poor transport or acclimatization, lack of oxygen, poor water quality). The parasite can be latent, waiting for a favorable condition (stress for example).
- Contagious: Very contagious (it is best to treat the whole aquarium).
- Severity: Serious if left untreated (high mortality rate). It is strongly advised to treat the whole tank and to strictly respect the recommended duration of treatment as its success depends on the elimination of free parasites (they are only then vulnerable when they escape from the skin and go in search of a host). Strains resistant to current treatments have unfortunately appeared recently.
- Occurrence: Fairly common. The parasite can be introduced by a new fish but also by plants or decoration. The parasite is most likely to infect the fish(es) after an episode of stress (sudden temperature variations, lack of oxygen, deterioration of water quality …). Changing water with water that is too cold can stress the fish and promote parasitic infection, so when doing water changes, try to match it as well as possible the temperature of the new water with the temperature of the tank.
- Treatments: Aquarium salt for a few days (see info box below) combined with a commercially available anti-white spot treatment: eSha Exit, JBL Punktol, Interpet Anti White Spot, Waterlife White Spot & Fungus, API Super Ick Cure , Sera Costapur, Tetra Contraspot, or failing that methylene blue (be careful as the latter can affect the plants and bacteria in the filter). It is generally advised to temporarily and gradually increase the temperature of the tank by two to three degrees during the treatment in order to accelerate the parasite’s life cycle.
- Note: Do not confuse these symptoms with the breeding tubercles (or breeding stars) of male goldfish (a handful of white dots that appear for a short time on the gill covers and on the leading edge of the pectoral fins: see Goldfish breeding section.
Aquarium salt: The addition of aquarium salt in addition to a commercially available treatment. Recommended salt dosage for goldfish: 1 tablespoon per 15-20 liters (4-5 US gallons) speeds up the process of eliminating the parasites that cause white spot disease and adds electrolytes to reduce osmotic stress. Be careful not to overdose the salt in the aquarium: it does not evaporate (after a water change, only add the dose corresponding to the volume of water that has just been changed). Also be careful when using salt if you have other species of fish in the same tank: some species are intolerant to it. Aquarium salt can be found in pet/fish shops, but any 100% natural non-iodised salt is suitable; do not use table salt! When the treatment is finished, partial water changes will allow the salt to be gradually eliminated.
Important: do not forget to remove the activated charcoal during the entire treatment (as it will absorb the medication). It can be put back in the aquarium at the end of the treatment to remove the residues.