Hydras as a problem in aquariums

Hydras are carnivorous and have stinging cells. They will compete with fish for live food. Although they are too small to eat adult fish, I wonder if they stress smaller fish like the Neon Tetra by biting them when they accidentally touch the hydras.

Another problem is simply that some people don’t like the way they look.

However, the biggest problem comes with infestations in the breeding tanks when people try to breed fish that lay eggs. The hydras eat the live food that is placed in the tank for the baby fish; multiply quickly and eat the baby fish.

There are several suggested ways to get rid of Hydra infestations. Most of these ways would certainly kill baby fish, and there are none that I consider safe with them. So if you expect hydras to be a problem, you need to get rid of them from your breeding tank before breeding.

Ways to remove Hydra

Fish

In a normal aquarium, what I like the most is to use fish that eat them. The most used is Blue Gourami.

Hot

A temperature of 41 degrees C (106 degrees F) for three days will apparently kill the hydra. It will also kill almost all types of fish, so it would be necessary to remove them. Some plants will survive this heat treatment.

Chemical products

Naturally, things like chlorine bleach kill hydra, as well as most other things. This can be used to sterilize non-living things like rocks, and has even been used successfully to destroy pests and diseases in entire aquariums. Of course, it will kill plants and fish. Considerable effort is needed to ensure that no residue remains before living things are reintroduced.

Aside from such drastic chemicals, there are several that can be used with fish, but not with absolute safety.

Copper can be used, but maintaining the correct level is difficult in a freshwater aquarium. Also, some studies suggest that many fish are more susceptible to copper than hydra.

Formaldehyde at 3 drops per US gallon it appears to kill most of the hydra without killing the fish. However, it may not kill them all with just one dose. Be aware that formaldehyde will lower the pH of the water as it breaks down into formic acid. The pH should be controlled and adjusted as necessary.

Flubendazole it is an anthelmintic drug. It will remove some internal parasites from the fish, as well as Hydra, ick (white spot), velvet, and gill flukes. Possibly the safest chemical Hydra will remove. A guide to the dosage needed is 1/2 gram of 10% flubendazole per 20 liters (5 US gallons).

With any chemical, remember that different types of fish likely have different tolerances, and different Hydra species can also vary considerably in their susceptibility to the chemical.

It’s also worth considering whether you really need to get rid of hydra from your aquarium. Normal maintenance; not allowing your aquarium to get dirty will help prevent a large build-up of Hydra.