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 to as large as 0.4 inches (1cm). Their colors range from translucent white to light brown, and green to yellow. Much like a sea anemone, hydra has a stalk or foot that attaches to surfaces (like plants, hardscape, or glass) and a mouth at the other end that is surrounded by long, wispy tentacles. These tentacles have stinging cells that are used to paralyze and catch their prey.
Scientists have long been interested in hydra because of their “immortal” cells and powerful regenerative abilities. Each fragment of a hydra can be regenerated to create a new individual hydra by being broken down. They can also reproduce sexually through the production of buds and eggs.
The green pigment of green hydra (Hydraviridissima), is due to a unique and symbiotic relationship between photosynthetic Chlorella alga.
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. They will quickly retract their tentacles if you touch them.
Are hydra bad for aquariums? Hydra are ambush hunters that like to eat microworms, insect larvae, and tiny crustaceans (e.g., cyclops, daphnia, scuds, and baby brine shrimp). In our experience, they are a natural part of the aquarium ecosystem and do not seem to greatly impact baby fish and shrimp populations. Fry are too large to be eaten and have a strong flight response, which causes them to flee from any stimuli, such as a stinging tentacle.
How to Get Rid of Hydra
It is usually not recommended to manually remove hydra unless you have a steady hand or a small population. Accidentally breaking off any hydra will cause them to grow into new hydra. We recommend that you first
Reduce food consumption
Going into the tank. Hydra that don’t have enough food will eventually starve and die. 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. Additionally, any potential predators larger than a hydra can be removed. 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. You can also consider treating live plants and decor before adding them to your aquarium, but do your research to make sure they will not adversely affect the plants and aquatic animals.
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