Jellyfish Bell Inversion

What is Jellyfish Inversion?

Technically called “eversion,” it’s defined as the process of turning inside-out. In jellyfish, eversion is when the outer perimeter of the bell has flipped up and over the top of the bell, creating a saucer or cup-like body shape. The oral arms of the jellyfish also hang down and are not tucked up under the bell, as per a healthy jellyfish.

[Note: “eversion” is when the bell is flipped inward; “inversion” is when the bell is flipped outward. “Inversion” is commonly used instead to describe this process in jellyfish.]

Common Causes

Here are things that can cause jellyfish bell eversion:

• Malnutrition leads to thin and weak jellyfish that are prone to flip
• Flow rate is too high causing the jellyfish to spin like socks in a dryer
  • This prevents jellyfish from belling or swimming naturally, which means they also are not eating properly, ultimately leading to malnutrition
• Flow rate is too low and the jellyfish are unable to bell properly due to the lack of “support” they get from the water movement
  • Belling problems always lead to eating problems—if they can’t bell properly, they can’t eat well, causing malnutrition (again) and creating thin, everted jellyfish
• Physical damage that occurs when a jellyfish becomes stuck to the bottom or side of the tank for over an hour, damaging their bell

Luckily, these are all fixable issues!

Solutions

Happy and healthy jellyfish should have rounded bells

Here’s how you can prevent eversion from happening:

• Feed only nutritious, neutrally-buoyant foods on a daily basis to maintain proper cell growth and function
• Adjust the flow rate just enough to keep the jellies off the bottom of the tank, but not so much that they are being propelled around the tank.
  • When trying to find the perfect flow, adjust your flow control valves and wait 20 mins between each adjustment to watch for a difference
  • Want to see an example of what proper flow looks like? Check out a few of our jellyfish aquarium videos on YouTube.
• Maintain the proper flow rate and the jellies will not have the opportunity to get stuck for long periods of time

Read more about the physical differences between HAPPY (healthy) and SAD (unhealthy) moon jellyfish on our Jellyfish Troubleshooting page.