Symptoms of body flukes include an excessive layer of slime on the body; isolation; clamped fins (fins laying flush against the body); scratching and flashing (rubbing its flank against the side of the tank, plants, or decorative tank objects); gills or fins which appear to have been eaten away; sores and ulcers as the result of the scratching. [2] X Research source Symptoms of gill flukes include gasping at the surface, irritation of the gills, gills covered in mucous, and visible irritation to the gil

To take a skin scraping, pick the fish up gently out of the water with a sock net. Hold the fish against the side of its bowl or tank. In your other hand, hold the slide at a 45 degree angle and press it down on the fish gently, pulling from the shoulder towards the tail. Always pull with the direction of the scales, never against, as this may hurt the fish. You should end up with some clear or opaque mucous on your slide. Once you have a sample, place a drop of water from the bowl or tank on top of the mucus. Place a cover slip over the slide. Examine your sample within the hour. [4] X Research source Take multiple samples to ensure there are no flukes present. You could detect flukes with a good magnifying glass, but the best way to see flukes is with a microscope at magnification of x40. Look for a translucent, ghostlike body moving about on the slide. Flukes have an elongated body with a rounded “head” and taper down to a pointed opisthohaptor (the organ it uses to latch onto the unsuspecting fish). You may see small hooks protruding from the fluke’s opisthohaptor. Depending on the species of fluke, they may or may not have eyespots. They are also extremely active; look for rapid elongation and contraction of the body.

Apply the mixture at a ratio of one gram per thousand gallons of water. Mix the solution well to speed its dissolution in the water. Aquarium salt will treat over seven known pathogens, and Dimilin or Program will eliminate all parasites except the fluke. With these other options rules out, you can safely conclude that your goldfish are suffering an infestation of flukes. [5] X Research source

A simple quarantine tank requires little more than a tank with a heater and a sponge filter. [7] X Research source You can add some water from the main tank into the quarantine tank to afford stressing the fish. Water from the top of the aquarium works best. Find a tank that has a dark bottom; if the tank is clear, place it on a dark mat or table. You could also add some artificial plants to give the fish something to interact with. [8] X Research source Ensure your quarantine tank is well-aerated, since the treatments applied often consume oxygen in the tank. Use an oxygen pump to ensure the tank receives a steady flow of oxygen. Over-oxygenating the tank is nearly impossible; unless your fish is wary of venturing near the bubbling area, or your pump is causing the tank to vibrate from the force of expelled oxygen, you are not adding too much to the tank. Unless otherwise noted, the following treatments all require isolating the affected fish in a treatment tank.

If employing Formalin-MS (a common formalin solution), use 20 drops per gallon of water (or 1 teaspoon per 9 gallons). Dip fish for up to fifty minutes. Remove fish from the tank if it shows signs of distress. Formalin can be used in quarantine tanks or in the main tank. A quarantine tank solution will contain 20-25 parts formalin per million parts of water. Depending on severity of the infestation, dip your fish in the quarantine tank for 12-24 hours. Remove fish after dip is complete and rinse in clean water. Return fish to its main tank. Repeat twice in three-day intervals. Formalin can be employed in the main goldfish tank as well as in quarantine tanks. However, when treating the whole tank with formalin as opposed to a quarantine tank, you must use a lower concentration. Mix 2 drops of Formalin-MS per gallon of water. Perform a 25% water change after 3 days and replace your filtration unit. Repeat two times, once every three days.

Do not use Methylene Blue in your main tank with the biological filter. It will destroy the bacteria living within the filter.

While common, this treatment is not always effective. Flukes lodged beneath the fish’s skin may be protected by the fish’s own mucous membrane. [10] X Research source

This is one of the few treatments which does not require 3-4 treatment sessions.

Praziquantel is the best option to treat flukes in goldfish. Mix 5-10 mg of Praziquantel per liter of water. Praziquantel may also be dosed in the fish feed. Apply 5 mg per kg of goldfish. Your veterinarian could inject Praziquantel directly into your fish. Ask your vet if this option is right for your fish. There are a multitude of medicines suitable for fluke-infested fish whose active ingredient is praziquantel. Prazipro Fluke tabs are a popular option, as is Droncit. [15] X Research source Other praziquantel treatments include Lifeguard, Tetra Parasite Guard, and Fungus Guard. [16] X Research source All are available at pet stores.

Acriflavine is also known as eufavine, gonacrine, neutroflavine, and trypaflavine.

Trichlorfon is the most common OP used to treat fish. Recommended dosages depend on the tank temperature. For temperatures above 27o C add 0. 25 mg per liter of water. For temperatures below 27o C add 0. 50 mg per liter of water. Another option is to mix Trichlorfon with water in a ratio of 0. 25-1. 0 parts per million. Dip fish in the mixture for one hour. Repeat daily for three days. Change 30-70% of the water between treatments and adjust the Trichlorfon level as needed. [17] X Research source

Four days after the final treatment, you may once again begin performing routine water changes.

Assuming you opted to treat the whole tank, your biological filter should be free of flukes. If you did not, use a praziquantel treatment on the filter for the prescribed period. If you are less cautious, you could choose to just rinse the filter well with dechlorinated water.

Even if you don’t see flukes, remain vigilant. They may have been reduced to a level you cannot detect. Pay attention in the weeks ahead to the behavior of your fish which may indicate they have returned.

Avoid adding new goldfish once you verify all the fish in a given tank are healthy. Recent research suggests that a closed community of goldfish will actually develop an immunity to flukes. [18] X Research source

A single goldfish requires 20-30 gallons of water depending on its particular species.