What is hydra and how do I get rid of it?
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 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. If a hydra is split into pieces, each fragment regenerates to become a new, individual hydra. They can also reproduce asexually by producing buds or sexually by creating eggs.
At our fish store, we like to use Merck's Safe-Guard liquid dewormer for goats (suspension 10%, 100 mg/ml), which contains fenbendazole as the active ingredient. Make sure to shake the bottle vigorously before treating the aquarium with 1 drop of medication per gallon of water. The medication works very quickly within 24 hours and has been safe to use with snails, shrimp, fish, plants, and beneficial bacteria in our experience.
For more information, read our full article on How to Get Rid of Hydra in Your Aquarium.