Low pH can have adverse effects on moon jellyfish over time, especially when it drops below 7.6. This problem is common in aquariums with filtration systems that don’t allow for adequate aeration or disturbance of water.
The optimal pH for moon jellyfish is 8.0-8.2. As pH lowers below this range, the water becomes more acidic and harbors excess carbon dioxide (CO₂). If prolonged, the lower-than-optimal pH can cause pitting in the bell, eversion, and bell shrinkage in jellies. Although moon jellyfish are commonly described as being “hardy” and “tolerant” of extreme water quality levels, too extreme can and will eventually cause them damage.
Filters that allow for splashing and rapid movement of water through them introduces oxygen to the system, keeping the pH up by steadily off-gassing that harmful CO₂. When filters are completely submerged in water, the rate at which the water is moving through them is little to none and can negatively affect both the water quality of your aquarium and the beneficial bacteria that you’ve worked so hard to grow during cycling. If the water isn’t moving through the filters, then the filters are doing nothing to clean the water. Adequate and efficient water flow through the filters is necessary for both the water quality and beneficial bacteria to stay in tip-top shape.
Luckily, this is an easy fix!
There’s all kinds of water conditioners, additives, and buffers on the market today that are specifically made to raise pH… for normal fish tanks, however. Since jellyfish are 96% water, they are a bit more sensitive to the chemical makeup of water than normal saltwater fish. So, adding in a bunch of chemical powders and liquids, especially into a small desktop jellyfish aquarium with less than 10 gallons of volume, isn’t always the best idea and can cause more harm than good! So, don’t do it!
Instead, we recommend the following tips to help keep your pH optimal:
Adding a bubbler is an easy and worry-free fix to raise pH. Bubblers (also known as aerators) constantly introduce oxygen to the water via bubbles. Most aerators include a valve or dial to alter the rate of bubbles giving you more control, which is even better.
It’s best to place the bubbler in the filter compartment, away from the pump, and as far down to the bottom of the tank as possible. This way, the bubbles are not being sucked into the pump and have a longer path to reach the surface, releasing a bit more oxygen into the water.
Note: You do not need an air stone, if one is included. These will only create smaller, erratic bubbles that have a higher chance of getting sucked up by the pump and into the jellyfish area – which you don’t want!
Always make sure your new saltwater has a pH of 8.0-8.2. This will help raise the overall pH of your aquarium and keep it up through weekly water changes.
We experienced this problem when working with the 6 gallon Cubic Orbit 20 jellyfish aquarium, as you can see in the video below that we put together some time ago.
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.]
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!
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.
As you populate your eon jellyfish tank with jellies, you may sometimes notice a jelly acting differently; belling oddly or sometimes infrequently. Is that jelly sick? Should you take some action to make it better? Not necessarily. First of all, jellies don’t get sick, per say; however, they can plateau in their development.
Take a look at your other jellies. Are they behaving in the same fashion as the jelly in question? Take some water quality readings and see if they are in range or not. Correct any levels that are off and wait a day or two. The jellies are 96% water. So, if your water quality checks out A-OK, then your jelly in question could be taking a personal day—having personal issues. This does not mean you need to take action on your whole system. If your water parameters are in range, be patient and keeping observing.
We have noticed over the years that sometimes a jelly will sort of plateau and change behaviors for up to two weeks and then get back to normal. Some jellies grow quick and fast and are always in action, but then their growth rate slows down and they can plateau. Some don’t grow at first and then take off later in life. Be patient with your jellies as they settle into your system and with your maintenance practices. It’s good to be on the ball observing their health and wellbeing; however, think about your tank as a system–an aquatic system. Don’t be quick to judge one or two “off” days with a jelly here or there. And do not go the route of forcing more food into the equation thinking that is the answer. Let nature do its thing and just maintain good water quality and maintenance practices. These guys are resilient and given the chance, they can rebound nicely in a well-kept environment.
Another thing to consider is that you are observing animals in a closed system and natural selection is taking place in front of your eyes! The stronger jellyfish will bell more, eat more food and grow faster and bigger. While, at the same time, the weaker jellies will grow more slowly and the very weak jellies will stay the same size as when you first introduced them, or will shrink. This is completely normal. We liken it to the “varsity”, “junior varsity”, and “bench warmers” of the jellyfish world. It is to be expected. In very rare cases will all the jellyfish remain the same size in a closed system.
…in some cases they take a personal day for the rest of their lives and there isn’t anything to be done. They can still eat and live and be just fine. Embrace the existentialists!!!