How to Get Rid of Hydra in Your Aquarium
You may have seen a tiny tentacle monster in your freshwater tank. It’s not a terrifying creature, but it is a fascinating freshwater creature called the hydra. Continue reading to learn more about hydra, and how you can remove them naturally without harming 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. Growing up to 0.4 inches (1 cm), they range in color from translucent white to green to light brown. 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 contain stinging cells, which are used to paralyze prey and catch them.
Scientists have long been interested in hydra because of their “immortal” cells and powerful regenerative abilities. Splitting a Hydra into smaller pieces will result in each piece regenerating to become an individual hydra. 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. If you have wild plants or live foods, hydra can be brought in.
Is hydra harmful to humans? The stinging cells of hydra are too weak to cause any harm to humans. If you try touching them, they will quickly retract your tentacles to protect themselves from predation by 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. 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 Hydra
Unless you have a steady hand and a very small population of hydra, manual removal is generally not advised. If you accidentally break off any pieces of the hydra, they will grow into new hydra. Instead, we recommend that you
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.
Hydra are particularly prominent in fry grow-out tanks and shrimp-only aquariums because we purposely overfeed them with hydra-sized foods like baby brine shrimp or powdered fry food. 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. Snails are great at cleaning up food left over after frying.
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.
Sign up for our weekly newsletter to receive educational articles and videos about freshwater aquariums.