Jellyfish are fascinating creatures. They are made of 90-98% water, yet they float along in the ocean mating and eating meat, something they share with many other animals.
The similarities stop there, but that doesn’t mean that jellyfish shouldn’t be studied in the wild, or even owned as pets. What do jellyfish eat in their natural habitat, and what do you feed a jellyfish you’re keeping in an aquarium? Let’s find out.
What do Jellyfish Eat in the Wild?
Jellyfish are an ancient and fascinating addition to the ocean habitat. They can survive in all kinds of salt water—cold water, warm water, deep water, and shallow coastal waters. They travel by pulsing through ocean currents, and they survive by quickly digesting their prey.
Digesting Their Food
That word “prey” is important. This indicates that jellyfish actually hunt and eat other animals, just like any predatory animal. How can a blob made of mostly water and little more than a few tentacles hunt, much less consume another animal?
The key is their ability to sting their prey. Jellyfish tentacles contain cells that sting their food, stunning the creatures motionless as they digest them. The top of the jellyfish, where its bell-shaped body resides, has a mouth located in the center. It is really more of an opening than a mouth like you think about a mammal having. Once prey has been stung senseless, the jellyfish moves its food into this hole and digests it quickly. The digestive process must occur quickly because jellyfish could not move around the ocean laden with a large meal in their bells.
Jellyfish void waste through this same mouth opening. Although this sounds disgusting to humans, jellyfish are not anatomically similar to any mammal, so this process is really quite interesting.
What Do Jellyfish Like to Eat?
But what exactly do jellyfish hunt in their long, dangerous tentacles? The answer is not surprising: mostly any living creature that is small enough to fit in their tentacles.
For example, jellyfish mainly like to digest plankton, crustaceans (like crabs and shrimp), fish eggs, small fish, the larvae of many sea creatures, even other jellyfish. Yet they will also eat small plants that they encounter in their travels.
Keep in mind that jellyfish aren’t active hunters. In fact, they are referred to as “passive” hunters, meaning they will take what they can get. They use their tentacles like fisherman use nets. As jellyfish swim, their bodies contract and expand to propel them forward. Each time their bells expand, this increases the surface area of their tentacle nets, landing them more prey.
When jellyfish gather together and establish a colony, it is referred to as a bloom. Jellyfish blooms are problematic for fisherman and other animals who have habitats in the area of a bloom. This is because the surface area of tentacle nets in a bloom can be quite vast, and jellyfish will eat everything they can catch in that area. This means that jellyfish consume the food of larger sea creatures, limiting what animals can survive after blooms move on. In this way, jellyfish can be dangerous for ocean habitats.
All in all, the diet of jellyfish in the wild is varied and diverse. Jellyfish will eat whatever will fit in their tentacle nets, as long as it is a living creature. Mainly, though, jellyfish eat the smallest members of the sea. Even though they aren’t eating everything in the ocean, jellyfish become problematic if they start a bloom because it will consume a lot of prey for other sea animals. Jellyfish can indirectly decimate the population of patches of ocean habitat even though they aren’t eating the largest creatures.
The Best Food for Jellyfish in an Aquarium
Life for jellyfish in an aquarium is quite different than in the wild. For one thing, their habitat is controlled. They can only eat what is delivered to their tanks. They are also mainly on their own in an aquarium, so they eat far less than a jellyfish bloom can. If you have jellyfish in your aquarium, or are planning to install a jellyfish aquarium, you need to know what food you can safely add to the tank.
Jellyfish Aquarium Food
Although it is not common to own a jellyfish aquarium, the trend is catching on. The most common type of jellyfish living in aquariums is called “moon jellyfish,” or jellyfish from the Aurelia genus. There are only two species of moon jellyfish available for consumers, and even those are hard to come by (Aurelia labiata and Aurelia aurita). However, if you happen to own some, you need to know what to feed them.
It is most common for jellyfish to be fed a mixture of different small sea creatures and seafood. Brine shrimp mixed with phytoplankton is a common dish for jellyfish, but you can also serve very finely cut up seafood. Commercially-produced jellyfish food is also starting to catch on, so you may be able to find jellyfish food prepared at the aquarium store or online. Look for frozen enriched Artemia nauplii, which is the common scientific name for brine shrimp.
Keeping Your Jellies Full
If jellyfish aren’t kept full, they can get skinny and sluggish. The good thing about jellyfish, something you don’t get with fish, is that you can see right through them. You can literally see if they have eaten or not.
For instance, if your jellyfish haven’t eaten in a while, you will be able to see just the clear, bluish tint of their bells. About 45 minutes after eating, you should be able to see the reddish color of food digesting right in the center of the bell. As long as you make sure you can see the reddish color of digested food inside the bell once a day, you know you are feeding them sufficiently. You don’t need to feed them more than this.
Do you know what to feed your jellyfish?
Jellyfish are fascinating, whether in an ocean or an aquarium. Maybe you’ve never considered keeping a jellyfish at home, but you love to watch them at the local aquarium. Did you know that they like to eat small shrimp and fish eggs?
If you’re considering installing a jellyfish tank at home, do your research so you can find a reliable food source. Jellyfish should eat everyday, and since they are passive eaters, they won’t necessarily eat as much as you think. Just watch their bells and look for the reddish glow of digested food. You’ll become a pro at feeding your jellyfish in no time.