How to Combat Hydra Infestation


 Hydras belong to Phylum Coelenterata, a group of aquatic organisms where jellyfish and corals also belong to. Hydra doesn’t just mysteriously appear in your tank. They are often introduced to the aquarium from an external source. Once inside the tank, the abundance of food sources will promote its growth and multiplication.

Aquarists often find Hydra a nuisance in their fish tanks, however there are also those that find them interesting and let them be. Hydra in tanks is often difficult to eradicate, however, it is not impossible.

Hydras are carnivores and compete with fish for live food. They are capable of rapidly reproducing asexually by producing buds that grow into new hydra. They are also known to prey on fish fry and small adult fish. The biggest concern associated with hydra is when they infest breeding tanks. Hydras eat live foods which are put into the tank for the hatchlings. With abundant food, hydras multiply quickly until such time that thy will prey on fish fry for lack of food.

Apart from the said reasons, there are hobbyists who want to get rid of hydras from their tank simply because they dislike the organism’s appearance.

Getting Rid of Hydra

There are several ways which have been proven to effectively remove hydra from fish tanks.

  1. Manual removal
    Physical removal of the individual hydra can be done when there is only a very small infestation. Make sure to soak artificial plants, rocks, and other tank decorations in 10% bleach solution for at least 10-15 minutes, scrub, and rinse with plain water, and air dry before putting back in.
  2. Adding predator fish
    There are species of fish that prey voraciously on hydra. These include Blue Gouramis, Mollies, and Paradise fish. Pond snails are also known to feed on hydra.
  3. Heat
    Before turning up the tank’s water temperature to at least 104F (40C) for about two hours, make sure to remove all your fish from the tank and relocate them temporarily. After two hours, turn the heat back down, lightly vacuum the tank substrate, and do a large water change (at least 50%). Before reintroducing the fish, make sure that the temperature has returned to the desired level.
  4. Chemical or medicinal treatment
    The use of chemicals or medicines to stamp out hydra from the tank should only be considered the last resort, when the other methods have failed to successfully eliminate the hydra from the tank. These substances may be harmful to the inhabitants of the aquarium including fish, live plants, and even the beneficial bacteria that acts as your biological filter. Some of the commonly used chemicals include Copper Sulfate and Potassium Permanganate. Anti-fluke medications, particularly those that contain formalin, can also be used to combat hydra infestation.

Preventive Measures

  • Since Hydra thrives well when there is plenty of food in the tank, strive to maintain a clean tank while avoiding overfeeding.
  • Live plants should be carefully inspected before these are added to the tank. You can also soak plants for at least 5-10 minutes in a solution composed of one quart water and a tablespoon of alum. Rocks and other aquarium decorations can also be soaked in the solution before being added to the tank. Make sure to rinse well using plain water after soaking.
  • Avoid collecting live foods directly from streams or freshwater ponds, for there is a possibility that you are also gathering hydra at the same time.

About the Author:

Peter Hartono is the founder and CEO of Just Aquatic - a proud Australian company that provides excellent online aquarium supplies for betta fish tanks, goldfish tanks and also aquatic plant care products carrying top of the line brands including API, biOrb and Exo Terra.