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 for more information about hydra. We also discuss natural ways to remove them from animals, plants and 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. 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 contain stinging cells, which are used to paralyze prey and catch them.
Hydra have long been a topic of interest to scientists due to their immortal cells and remarkable regenerative powers. If a hydra is split into pieces, each fragment regenerates to become a new, individual hydra. They can also reproduce asexually, either by creating buds or eggs.
Green hydra (Hydra viridissima) has a unique, symbiotic relationship with photosynthetic Chlorella algae, which is responsible for 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. Hydra can also be introduced if you collect live foods, plants, or hardscape from the wild.
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 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. Adults are too large to eat, and fry have strong flight responses that cause them to run away from any stimulus like a stinging tendacle.
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. 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.
Another natural removal method is to add predators to eat the hydra. 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. 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. It is possible to treat live plants or decor before you add them to your aquarium. However, make sure to do your research to ensure that they are safe for aquatic animals and plants.
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