"Parasites come in a range of sizes but generally can only be seen under a microscope"

Fancy Goldfish parasites can come in different forms, some honourable mentions are: Costia, flukes, anchor worms, white spot and trichodina. It's best to identify which type of parasite you have with a microscope before treating. Below are treatments and dosage rates to use dependant on the parasite. 

  • Anchor worms - Are external copepod parasites that attach to your fish under their scales. These parasites have multiple non-parasitic stages that take place in the water. Once a male mates with a female, she attaches to a fish to mature into a reproductively active adult. These parasites get the name "worm" from the extending female reproductive structure. Juveniles will be free-swimming in your aquarium, but will not be a nuisance for your fish. Treating anchor worms with organophosphates or diflubenzuron (dimilin) is effective, but needs to be undertaken with severe caution. Waterlife Parazin P Parasite Treatment is safe and effective for fancy goldfish.

  • Flukes - Can affect the body (body flukes) and gills (gill flukes) of a goldfish. If it goes untreated, flukes can destroy the gills and kill the sick goldfish then, infecting other goldfish in the tank. Under a microscope, flukes resemble a small worm with gill flukes containing the next generation within it. Effective treatment can consist of Fluke solve or Fluke P which will have no impact on your biological filter system and, a second dose may be required 7 days later.

  • Whitespot - Is one of the easiest parasites to diagnose, even by novices, as the fish become covered in tiny white spots. The fins are usually affected the most. The spots are actually cysts formed over the parasite itself, which isn’t visible to the naked eye.  A severely affected fish will be visibly lethargic and, flicking or clamping its fins. If left untreated, white spot can quickly kill a fish and spread to others in the tank. Treatments like Malechite are effective at killing white spots, coupled with other methods like turning up the water temperature to 30°C/86°F, as this speeds up the life cycle of the parasite and eliminates it if the temperature is held at this temperature over 5 days. Also, adding salt at 3ppt, which nine out of ten parasites don’t like.

  • Costia - can resemble the symptoms of tricodina or flukes and because the parasite is so small, 8-15 micrometres across, it is hard to confirm a diagnosis without taking scrapings and viewing them under a 300-400x microscope. Symptoms include: clamped fins, loss of appetite, slime patches on body and fins, laboured breathing and flashing. Treatment can consist of Formalin or Potassium permanganate. Salt at 9ppt can also be effective to numerous strains of costia but, all treatments need to be conducted very carefully and via the instructions of the manufacturer.

  • Tricodina - Usually, healthy fish can control small numbers of the parasites, but in severe conditions and in large numbers, Trichodina can run down your goldfish's immune system and open a door for other complications such as ulcers or other secondary bacterial infections. Symptoms include: clamped fins, loss of appetite, laboured breathing and flashing. The best treatment is using the same medications as you would to kill white spot. You can use the salt treatment or medicated treatments like potassium permanganate or Malachite Green with Formalin.

  • Fish lice (argulus) - Reproduce by laying eggs in long strings on any hard substrate. Female parasites start laying their eggs in water above 10ºC and eggs take 16 days to hatch at 20ºC, but longer in colder temperatures. The fish louse will attach onto the goldfish and cause physical damage to the mucus and epidermis, leading way for secondary bacterial or fungal infection to occur. Fish lice are common in newly imported fish and also fish that have been living in outdoor ponds. Lice should be treated in the same way anchor worms are. Visible lice should be carefully removed with tweezers and then the system should be treated with organophosphates or diflubenzuron (dimilin). Waterlife Parazin P Parasite Treatment is safe and effective for fancy goldfish but, a repeat treatment may be needed to kill eggs.


"Acriflavin is a great gentle medication to have in your medicine cabinet and has helped me multiple times."

Bacterial and fungal problems can occur more often than not in fancy goldfish aquariums and ponds especially when the fish's immune system is weak.

  • Bacterial - Removal of a fish's protective mucus membrane or scales during netting is a common cause. Bacterial infections manifest in many ways, but common signs include a white film on the fish's body or fins, cloudy eyes, tattered fins, and haemorrhaging (bloody patches) or open sores (ulcers) on the body and mouth. Bacterial problems can cause further complications like ulcers and even dropsy. Aquarium salt can be used alongside antibacterial medication like Acraflavin or Chloramine T. Methylene blue is effective for secondary infections and fungus but both methylene blue and Chloramine t are very destructive on biological filters.

  • Fin rot - Is a common disease that describes the rotting or fraying of a fish’s fins or tail. If you suspect that your fish may be suffering from fin rot, take a close look at their fins and tail for the following symptoms: fins or tail appear to have frayed edges, the fin or tail edges have turned white, or even black and brown in some cases and/or, inflammation at the base of the fin. These symptoms are often accompanied by a loss of appetite, less activity, and your fish sitting at the bottom of the tank. Treatments can include Acraflavin or formalin/malachite green and, Waterlife myaxin if very effective.

  • Fungus - Also known as cotton wool disease, is one of the more common goldfish diseases, although, the fungus doesn’t tend to affect healthy fish.  If a fish has sustained an injury, this can give fungus the opportunity to invade the area. Prolonged low water temperatures may make fish prone to fungus attacks as it often occurs in early spring, late autumn and winter. Treatment is fairly straightforward with Methylene blue bath and salt baths or treatment of Malachite green. Also, ensure the water parameters are good and stable and, raise the temperature slowly to increase the fish's metabolism. There are many off the shelf treatments available such as the water life fungus and white spot treatment. 

"Water treatments like Seachem prime are great to have on hand where water parameters are unstable."

Water treatment are generally used by most hobbyists, especially in the western world of goldfish keeping. 

  • Dechlorinators - like Seachem prime, it can provide numerous benefits and, may be used during tank cycling to alleviate ammonia/nitrite toxicity. It contains a binder which renders ammonia, nitrite, and nitrate non-toxic, allowing the biofilter to more efficiently remove them. It will also detoxify any heavy metals found in the tap water at typical concentration levels.

  • Calcium Montmorillonite (bentonite) Clay -  has been used in the hobby for many years. It’s packed with upwards of 60 bio-available minerals and trace elements, plus anti-bacterial, anti-fungal, and anti-parasite properties. Breeders who used it reported: it improved colour, healthier skin, scales and skeletal system, improved immunity, including disease & parasite resistance, increased egg production, fewer deformities and enhanced growth rates; amongst other benefits.

Water Treatments

Salt... the Holy grail?

"PDV salt can be up to 90% cheaper than purchasing from an aquarium brand! Click below to find out how it saved my goldfish from dropsy"

Is salt really the holy grail of all fish treatments? Well, I think it is! Here's why:

Salt can: be used to treat a multitude of parasites

  • lower nitrite and ammonia toxicity 

  • increase fish mucus production, protecting them from parasites 

  • reduce pressure on the osmoregulatory functions and tackle dropsy

  • help kill bacteria and increase the healing of ulcers and infections

If you want to know more about using salt, then please check out my in-depth help guide below.

Goldfish treatments