How to Kill Planaria in an Aquarium

Written by jason williams
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How to Kill Planaria in an Aquarium
Planaria infestations are quite common in shrimp aquariums due to overfeeding. (Jupiterimages/ Images)

Planaria are small flatworms that often take up residence in aquariums. These creatures -- usually sustained by the overfeeding of resident fish -- are extremely difficult to get rid of once a population becomes established. Since planaria can survive even when split into pieces -- in which case each piece becomes a new flatworm -- and are too small to be easily captured, the best course of action is to carefully use chemicals to kill off the current infestation. The prevention of polluted conditions in the tank will help avoid new infestations.

Skill level:

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Things you need

  • Fenbendazole (dog de-wormer powder)
  • Gram measuring spoon
  • Substrate siphon

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  1. 1

    Buy fenbendazole powder; the product is available from most pet supply stores. Measure out 0.1g of powder for every 10 gallons of water in your tank. Crush the powder as finely as possible with the bottom of the spoon.

  2. 2

    Remove the filter cartridge if it contains activated carbon as the carbon will remove the fenbendazole from the tank before it can be effective. Apply the fenbendazole to the tank and carefully stir it to aid it in dissolving.

  3. 3

    Wait 24 hours and check the tank to see if all of the planaria are dead. Apply another dose -- again, 0.1g per 10 gallons of water -- if living planaria are seen. Wait another 24 hours and observe the tank again.

  4. 4

    If living planaria are still seen after two doses, replace the carbon filter and allow the tank to sit untreated for 24 hours. After 24 hours have elapsed, remove the filter cartridge again and add another dose to the tank. This time, however, add 0.15g per 10 gallons of water. Continue gradually increasing the dose by an additional 0.05g per every 10 gallons of water until the planaria are exterminated. Be sure to allow the tank to sit untreated between dose increases, however.

  5. 5

    Replace the filter cartridge. Use a small siphon to suck up any dead planaria that you can find.

Tips and warnings

  • Reduce feeding to prevent reinfestation; only feed fish what they can eat in five minutes, and only feed shrimp what they can eat in two hours.
  • If you have sensitive fish, start with an initial dose of 0.05g of fenbendazole per 10 gallons of water and work your way up. It's better to take it slow than risk harming your aquarium species.
  • Fenbendazole treatment also works for hydra, another common aquarium pest. In the case of hydra, the fenbendazole should be applied directly to the creatures with a siphon or eyedropper.
  • Measure the initial dose of fenbendazole very carefully; starting with too high of a dose can easily kill other fish and shrimp along with the planaria.

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