How to get Rid of Hydra in Your Aquarium

How to Get Rid of Hydra in Your Aquarium

A miniature tentacle-monster has been spotted in your freshwater aquarium. Not to worry – it’s a fascinating freshwater creature called hydra that is relatively easy to deal with. Keep reading as we talk about what is hydra and a few natural methods of removing them without harming your animals, plants, or beneficial bacteria.


What is Hydra?

These tiny, freshwater organisms of the genus Hydra are the distant relatives of jellyfish, corals, and sea anemones. They can grow up to 0.4 inches (1 m) in length and range in color from translucent to light brown to green to dark brown. Similar to a sea anemone’s hydra, it has a stalk, or foot, that attaches on surfaces (like glass, plants, hardscape, and glass), and a mouth at one end that is surrounded in long, wispy, tentacles. These tentacles have stinging cells that are used to paralyze and catch their prey.

Hydra have long been a topic of interest to scientists due to their immortal cells and remarkable regenerative powers. Splitting a Hydra into smaller pieces will result in each piece regenerating to become an individual hydra. They can also reproduce asexually, either by creating buds or eggs.

Hydra viridissima, also known as green hydra, has a unique relationship with photosynthetic Chlorella, which is responsible to its green pigment.

How did hydra get in my fish tank? In our experience, we’ve noticed that hydra often lays dormant in fish tanks for many months, but then the population blooms when you start heavily feeding baby brine shrimp. You can also suspect that the hydra may have gotten into your fish tank from decorations, rocks, driftwood, or aquatic plants that were infected. You can also introduce hydra if you get wild foods, plants, and hardscape.

Are Hydra dangerous for humans? No. The stinging cell’s power is too weak to harm humans. If you try to touch them, they quickly retract their tentacles and ball up to avoid predation from larger animals.

Are hydra harmful to aquariums? Hydroplanes are predators that eat microworms and larvae as well as tiny crustaceans like scuds and scuds. In our experience, they are a natural part of the aquarium ecosystem and do not seem to greatly impact baby fish and shrimp populations. Adults are too big to be eaten, and fry have a strong flight response that causes them to jerk away from any stimulus, like a stinging tentacle.


How to get rid of Hydra

Manual removal is not recommended unless you are able to hold a steady hand with a small number of hydra. You can accidentally cut off any hydra pieces and they will grow back into new hydra. Instead, we recommend that you

Reduce food consumption

going into the tank. When hydra don’t get enough food, the majority of them will starve to death and eventually disappear. Consider target feeding the fish or using feeding dishes for shrimp to prevent the food from spreading throughout the aquarium. Regular water changes and gravel vacuuming will reduce the number of fish to an almost unnoticeable level.

A natural method to remove the hydra is to introduce predators. You can try just about any omnivorous or carnivorous fish that is small enough to notice the hydra – such as guppies, mollies, betta fish, paradise fish, and gouramis. If the fish do not seem to consume the hydra, try reducing feedings to whet their appetites.

Aquariums with adult fish and snails rarely get large hydra populations because hydra is a convenient source of live food.

We purposely feed hydra with baby brine shrimps and powdered fry foods to make them more prominent in shrimp-only aquariums and fry grow-out tanks. We usually get rid of any predators that might eat both fry or hydra. Luckily, you can add snails (like ramshorn, pond, and spixi snails) that are happy to consume hydra but are too slow to go after baby fish and shrimp. The snails are also great at cleaning up any food that has not been eaten by the fry.

People often prefer to use chemical treatments (such as deworming agents or planaria remedies) to kill hydra, but many of these methods are not safe for snails, shrimp, fish, plants, and/or beneficial bacteria. If you are looking to add live plants to your aquarium, it is worth researching to ensure they do not harm aquatic animals or plants.

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