Jellyfish in Freshwater

Q. I was wondering if there is any species of jellyfish that could live in a freshwater aquarium. I think jellyfish aquariums are really neat, but I only have a freshwater aquarium.
Janet Biggar
Eerie, Indiana

A. Yes, there are jellyfish that inhabit freshwater. The species I am most familiar with is Craspedacusta sowerbyi. They are a freshwater jellyfish that inhabit nearly all continents, but they are very rare in Africa. The United States did not report any of these animals until 1908. As of February 2000, they had been reported in 43 of the 50 states. These animals are freshwater cnidarians that inhabit lakes, reservoirs and even manmade basins like flooded rock quarries. Although these animals are very ecologically diverse, they tend to prefer calmer water, in a reservoir or lake to the rough and turbulent environment of a river.  

Sadly, I don’t know of any person who has kept C. sowerbyi in a home aquarium, and I don’t know of any fish outlet that would sell the animal. Being such a specialized animal, it is hard for me to recommend any aquarium necessities for it. I do know these jellyfish tend to lie on the bottom of whatever water body they occupy, conserving their energy for prey capture and reproduction.

Freshwater jellyfish typically eat zooplankton from the water column. Using their nemocysts, they sting prey in the water, stunning it and allowing for easy entry into the animal’s body. These jellyfish have also adapted well for cold water. During colder months, the animals close up and become nearly dormant until water temperatures rise.

From what I have read, freshwater jellyfish are very difficult to keep in the home aquarium. One thing to do is to make sure you have a filtration system that will not suck the jellyfish up into the filter. My assumption is that sponge filters would work best. Also, make sure you do not have a strong current moving through the aquarium. The main point to make note of is jellyfish require a constant food source; brine shrimp and Daphnia are highly recommended.

Other than that, I cannot find much information about keeping freshwater jellyfish. My guess is not many people are keeping jellyfish, and those that are likely shoot for the marine animals as opposed to those found in freshwater. One nice point about C. sowerbyi is they lack nemocysts strong enough to pierce human skin. In that regard, they are somewhat safer than their marine cousins.