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You might have thought you were feeding the best food? Or didn't know which one was best? Here's how to tell!

Fish Health - SupaVerm


A Closantel/Mebendazole combination (Supaverm) was tested in eight discrete systems on several species of fish, with Goldfish and Koi in the majority. Within five to seven days from the first applications of Closantel/Mebendazole combination, and replicated in eight different systems, every member of every species of goldfish was 100% annihilated including Ranchus, Pembrookes, Midnights, Wakins, Telescopes, Shubunkins and Comets. Salt appears to enhance the killing effect of Closantel/Mebendazole combination on flukes. Carbon does not remove sufficient compound to save the Goldfish in treated systems. There appears to be no negative effect of Closantel/Mebendazole combination on Koi. Closantel/Mebendazole combination was 100% effective in the eradication of flukes in all systems in less than 36 hours without negative effect on plants, Koi or filter.

Body of Article:

Research finished up on Closantel/Mebendazole combination years ago, branded "Supaverm" from the UK. We're going to watch all surviving treated fish for signs of toxicity for several more weeks. We are not tracking changes in blood parameters. This would be interesting if funding was available.

"Supaverm" is the trade name of a nematode and cestode treatment from Janssen Animal Health. The active ingredients are Closantel (5mg/ml) and Mebendazole (75mg/ml).


Mebendazole belongs to the chemical group of benzimidazolecarbamates. Its full chemical name is: Methyl 5-benzyl-1H-benzimidazole-2yl-carbamate.


This is a new broad-spectrum anti-parasitic medicine. It is especially effective against nematodes and cestodes, including hepatic flukes. Closantel's full chemical name is: N-[5- chloro-4-[(chlorophenyl)cyannomethyl]-2-methylphenyl]-2-hydroxy-3,5-diiodobenzamid. Molecular formula of Closantel is C22H14Cl2I2N2O2

Mr. Chuck Downs had read with interest the reports from the UK concerning this compound and made arrangements to provide us with some Closantel/Mebendazole combination for testing purposes.

He writes: "Recently, I've discovered that koi keepers throughout the UK and even some of the breeders in Japan have been using a new treatment for flukes called Supaverm. From what I know, Supaverm is actually a 'sheep dip', and contains Closantel at 5 mg/l and Mebendazole at 75 mg/l as the active ingredients. The results look fantastic, with universal 100% elimination of flukes, with only one treatment (adults, eggs, etc. all wiped out)".

"The nice part is the dosage is extremely low (2.2 ml per ton, or 1000 liters). Since my pond is 22,000 gallons (roughly 85,000 liters), that only amounts to 187 ml to treat my pond. A gallon of the stuff costs around $50 US, but I think you can only get it in the UK."

The Systems:

Eight systems were treated with Closantel/Mebendazole combination.
System One:
(150 gallon)
(1) Red tail catfish 22"
System Two:
(150 gallon)
(8) Koi varying from 5" to single specimen of 18 inches.
(12) Pembrooke Goldfish
(7) Wakin goldfish
System Three:
(150 gallon)
Pacu, Alligator snapping turtles.
System Four:
(10 gallon)
(4) Shubunkin Goldfish
System Five:
(10 gallon)
(4) Shubunkin Goldfish
System Six:
(10 gallon)
(4) Shubunkin Goldfish
System Seven:
4000 Gallon pond
Koi and Koi:Comet hybrids
System Eight:
300 gallon pond
(12) Ranchu Goldfish breeder adults
(2) Small Koi

Systems one through three were also treated with 0.3% salt.
Systems four through six used carbon in their filtration.

Regimen Used:

Each system was populated with fish. In all of the systems containing Koi or Goldfish, the presence of flukes was confirmed by microscopic biopsy of skin, gills and fins. The systems with the other fish were included to test the safety of this compound with unknown (heretofore untested) species of fish.

The U.K. dose of this compound is 1 ml per 90 British gallons. We dosed 1 ml per 100 US Gallons.

On Day one, each system was treated with the equivalent of (1) one-milliliter of Closantel/ Mebendazole combination suspension per 100 US Gallon of water.

In systems one through three, no second treatment was needed for the flukes. Microscopic biopsy confirmed that the flukes were entirely gone within only 12 hours. Ich remained on these fish for three more days and disappeared.

In systems four through six, a second biopsy at the twelve-hour mark showed abundant flukes. These systems were not salted, and they contained carbon. It is possible that the carbon removed some of the Closantel/Mebendazole combination, or more likely; that the salt accentuates the Closantel/Mebendazole combination effect on the flukes.

In systems four through six we re-applied the Closantel/Mebendazole combination at double strength, twenty-four hours after the first application. After twelve more hours, flukes were completely gone from treated fish.

Well, that's where the story normally would end, and I sent out a message hearkening the "beginning of the end" for Flukes. To the day, seven days after the first treatment in systems one through three, the goldfish began to die in threes and fours with almost no symptom except lethargy, slowed respiration and reaction-time, plus excess slime coat.

System four through six were set up all at the same time in parallel, and those fish died within five days of application. (Higher dose used results in speedier kill?)

System Seven and eight saw the end of all resident goldfish two days later. (I had waited to treat these systems with Closantel/Mebendazole combination for 48 hours to see if the drug would be toxic.)

System Seven contained Goldfish-Koi hybrids, and these hybrids are still alive eleven days after the first treatment.

No Koi was adversely affected by the Closantel/Mebendazole combination.

100% of Goldfish treated are dead. They died in each system over 36 hours from start to finish with 100% morbidity and 100% mortality.


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