Introduction A guide to caring for your Moon Jellyfish
This guide is built upon several years of observation and care for many moon jellyfish bought from a variety of sources. Initially this guide was intended for owners of the original Jellyfish Art desktop tank, but it has expanded into a general care guide regardless of tank type. It has been supplemented with reading material in several other books and websites. I hope my experiences can provide a starting point to reduce the difficulty for anyone else. Feedback, corrections, or general correspondance are welcome and appreciated. This guide was last updated on June 5th, 2022.
Environment How to determine if your water is appropriate for Moon jellyfish
Jellyfish can survive outside these ranges but the further away from ideal, the greater the risk to the jellyfish should anything go awry. Jellyfish can technically survive in water that is up to 4.0 ppm total ammonia (NH3/NH4+) and 80.0 ppm nitrate (NO3-), but the aquarium water should be changed as soon as possible for the long term health of the jellyfish. The term total ammonia refers to both ammonia (NH3) and ammonium ions (NH4+); more information can be found on the internet explaining how the pH of your tank water determines the equilibrium balance between toxic ammonia (NH3) and less toxic ammonium (NH4+).
For comparison, an ammonia level of 4.0 ppm would kill a fish within hours. If the aquarium water climbs above 2.0 ppm total ammonia (NH3/NH4+), change the water more frequently until the bacteria in the tank catch up and reduce the ammonia to acceptable levels. For more information, read about the nitrogen cycle for marine life on the internet and read about the ammonia (NH3) -> nitrite (NO2-) -> nitrate (NO2-) transformation.
|Parameter||Ideal Range2, 3, 7|
|pH||8.0 - 8.3|
|Salinity||32 - 35 ppt|
|Ammonia (NH3)||0.0 ppm|
|Nitrite (NO2-)||0.0 ppm|
|Nitrate (NO3-)||20.0 ppm or lower|
Water Maintenance Tips and tricks to safely change tank water
Water changes should be done as often as necessary to keep the tank parameters ideal for the jellies. This will depend on your tank; the Jellyfish Art and EON tanks both are suitable for one to two water changes a week. If you have any additional animals, you may have to change the water more often depending on their diet. Animals that eat leftover jelly food will remove chemical energy that heterotrophic bacteria would normally convert into ammonia. Although these cleaner animals also release ammonia, it will be less than if the food was left to rot. However, animals that eat algae are not removing chemical energy from the uneaten food. The algae only grows once the food has been converted into ammonia, then nitrites, then nitrates (which the algae consumes). You will need to change water in your tank more frequently if you have extra animals in the tank.
Freshly mixed saltwater is a potential hazard to your animals for two reasons. The first is any undissolved salt crystals may cause osmotic shock to moon jellies, which cannot handle salinity differences well.5 Secondly, freshly mixed seawater has not reached its oxygen/carbon dioxide equilibrium, and that also leaves the potential for either pH shock or corrosive oxidation.10 Jellyfish are mostly water, and are not well protected against this unlike other marine animals. If you have snails, you may see them secrete a brown sludge or ooze and tuck into their shells for several hours. After time passes, this ooze will harden into a film and then peel off. Airing the water out lets the saltwater reach a steady state and avoids chemical reactions that will harm the animals.
Do not be alarmed if your water is cloudy; it is likely caused by the beneficial nitrifying bacteria that break down ammonia (NH3) and nitrites (NO2-) into nitrates (NO3-). Over time, the water circulation will cause the bacteria to stick to the substrate and they will begin to multiply.8 Nitrifying bacteria reproduce relatively slowly, taking approximately 15-20 hours to double in population.8
If you have removed more bacteria than you'd like, you may purchase a bottle of Fritz-Zyme 9, Fluval Cycle (formerly Nutrafin Cycle), Instant Ocean BIO-Spira, Prodibio BioDigest or any other bacteria seeding product and add additional bacteria into your tank. A post by Jellyfish Art on their Facebook page implies that their live rock shipped to customers is simply live rock dosed with Nutrafin Cycle. After using all of the above, I think that they all do a passable job. Some may be better than others, but it will not matter in the long run.
Feeding How to ensure your jellyfish get the necessary nutrition
The nematocysts are part of how the jellyfish stimulates itself into movement; feeding properly is an important part of making sure the jelly is cared for in the long-term.2
The feeding procedure is relatively simple. Gently and slowly squirt food into the tank, and away from the jellyfish. You will need to adjust the food dosage so that enough is caught by the jelly, as well as siphoning out uneaten food to avoid fouling the tank. Feed your jellies once per day. Jellies can miss feeding for many days without dying, but make sure to feed them twice per day for every day of missed feeding. If you have the time, you may also divide the day's food into multiple feedings per day.
The jelly should retract its oral arms and slowly (over the next 5-30 minutes) have the food travel up the oral arms and into the four stomachs in the bell.
If the food is bunching up at the mouth but not traveling into the four stomachs, check the pH of your tank. A pH that is on the high side of the acceptable range (e.g. 8.4) may cause the cilia that move the food into the stomachs to not function as effectively.
If that does not solve the issue, check your food source. You may have rotten food or inappropriate food material. Try a different source; many retailers that sell jellies also sell their own food packages. See to the right for some sources.
If you are not already using a reef salt with calcium and alkalinity present, consider switching (see above). The minerals present in reef salt are naturally present in seawater and are useful at moderating the pH from becoming too high or low.
250g of frozen Artemia from Moonjellyfish.com
2oz of Golden Pearls from Brine Shrimp Direct
Health and Exercise How to prevent your delicate jellyfish from coming to harm
Accordingly, jellyfish are delicate; being sucked through the substrate, air channel, or filter box (exactly which depending on what tank is owned) is harmful. If you own an original Jellyfish Art tank, you can avoid this problem by ensuring there are no pieces of live rock or substrate are blocking the air channel at the base of the tank, causing a strong point of suction. If your jellyfish are being sucked into the air channel from the top, this is caused by the air channel being completely blocked at the bottom of the tank. Gently clear out the substrate and live rock gravel at the bottom, taking care not to touch the jellies. If you prefer, you can gently scoop them into a clean container for safekeeping while you perform this maintenance.
If harm does come to your jellyfish, do not panic. While they are easy to damage, jellyfish are difficult to kill. With care, your jellyfish can make an incredible recovery.2 Holes and large tears in the bell are recoverable so long as your jellyfish has not reached advanced age.4 Even if your jellyfish cannot eat or swim, it can still heal. Jellyfish can survive weeks without food, they will shrink and use up their bell mass to heal. Sadly, damage on older jellyfish (i.e. larger jellies) will cause jellies to scrunch up as they heal, permanently disfiguring the jellyfish, although it can still eat and survive.
The first things a jellyfish regenerates are to repair its bell and regrow its oral arms. As a last resort, you can move it into any clean glassware and dump in a dose of nitrifying bacteria (Fritz-Zyme 9, Fluval Cycle, etc.) to help eliminate ammonia. I personally do not recommend feeding them unless you are willing to completely change out the water in the dish and reacclimate them every time (or precisely measure your water and salt to ensure identical salinity every time). A badly damaged jelly typically cannot eat anyways, and the cramped environment will generate ammonia to a harmful level quickly. Although this approach has tradeoffs, I still recommend it. Your jelly will lack a current to help it keep shape (increasing risk of eversion) but your jellyfish will avoid further damage if it has trouble swimming due to damage.
If your jellyfish is beginning to flip inside out (e.g. jellyfish eversion syndrome), there are several potential causes:1, 3
- Dramatic salinity change
- Dramatic temperature change
- Poor water quality (ammonia, nitrites, nitrates)
- Lack of proper nutrition (diet is lacking nutrients, or food not getting into stomachs)
If your jellyfish is a brownish color, it means the jellyfish is of advanced age and is approaching the end of its natural lifespan.1
- Turn off your air pump to avoid having the jellyfish sucked through the air channel while you rescue them.
- Gently swirl your feeding pipette three times in a horizontal circle above the jellyfish to create a vortex current that will lift the jellyfish up out of the substrate. Go slowly, and be patient, it will take several seconds before the vortex occurs. If nothing happens, try again slightly faster. (Via Brian Rogers)
- If that does not work, try gently squirting water into the substrate next to the jellyfish to lift it up. Again, be gentle, your jellyfish may be "glued" to some rock, and being gentle will save its oral arms from being torn off by the force the water.
- If that does not work, you may have to stick your hand into the tank and gently remove some pieces of substrate before trying again. Try not touch the jellyfish directly with your hands or the feeding pipette
Retailers Where you can buy jellyfish tanks and animals
|Moon Jellyfish / Sunset Marine Labs||Small (1"), Medium (2"), Large (3")||Sunset Marine Labs has over 20 years of exprience captive breeding moon jellies down in the Los Angeles area. The owner, Nancy Sowinski, has supplied jellies to aquariums, and commercial establishments world-wide. This experience allows Sunset Marine Labs to give exact directions on how to care for them. In addition to the standard arrive alive guarantee, the company has (for now) an unofficial policy of shipping one extra animal in case something dies in transit. Although it is always possible to receive a damaged animal due to the shock of shipping, I have had a full recovery every time.|
|Pet Jellyfish||Small (2.5cm or 1")||Pet Jellyfish is one of the only UK suppliers of moon jellies, making them a valuable supplier for any European owners of jellyfish tanks. In addition, they sell various other species of jellyfish (blubber, sea nettle, etc.).|
|Jellyfish Art||Small (1.5"), Medium (2"), Large (3")||Jellyfish Art is a 6 year old company that was originally founded in San Francisco. After five years, the company was sold and relocated to Florida. Initially their specimens were wild caught, which led to issues with temperature acclimation and care. My initial purchase included at least two different species of moon jelly. They are currently working on a captive breeding program, but for now are acquiring their jellies from others. Jellies bought from Jellyfish Art are generally "wild cards", size may differ from advertised, and it is unknown what their true origin is and whether they are suited for the warmer household temperatures.|
|PB'N'Jellies||Out of business||PB'N'Jellies was founded by Wyatt Patry, a former senior aquarist at the Monterey Bay Aquarium responsible for the jellyfish exhibits. Wyatt Patry made a breakthrough at breeding Crown jellyfish in captivity. PB'N'Jellies was Wyatt's business selling moon jellies, in addition to an aquarist blog that he maintains. Unfortunately, the company has closed down as of 2017, although Wyatt is still at the Monterey Bay Aquarium.|
References Additional information and where I found it
- How to Keep Jellyfish in Aquariums: An Introductory Guide for Maintaining Healthy Jellies by Chad L Widmer
Chad was the head curator of the jellyfish exhibit at the Monterey Bay Aquarium and his book is intended to help owners raise and breed their own jellyfish. Includes a few useful practical tips on what to do and what not to do, as well as a troubleshooting guide.
- Nancy Sowinski
Nancy is the owner of Sunset Marine Labs, and their retail division Moon Jellyfish. With 20 years of experience, she has provided moon jellyfish to a variety of aquariums, restaurants, and clubs world wide.
- Cubic Aquarium Forums
This European company has a resident jellyfish expert dubbed Dr. T who also has contacts at a Japanese university. Their forums are full of detailed information and advice on keeping jellyfish.
Wyatt Patry is a senior aquarist at the Monteray Bay Aquarium, and was responsible for the breakthrough that allowed Crown jellies to be bred in captivity. He owns PB'N'Jellies, a Moon jelly supply site.
- Tank Raised Moon Jellyfish by Jim Stime, Jr.
This article is written by Jim Stime, the designer of the Jelliquarium, an early home aquarium for jellyfish. The article contains a great detailed overview of what raising a large number of Moon jellyfish is like.
- Aurelia Aurita
Wikipedia article on Aurelia aurita, also commonly known as the Moon jellyfish.
- Sunset Marine Labs Video: Acclimating Your Jellyfish Properly
This video by Moonjellyfish.com (the retail arm of Sunset Marine Labs) shows how to acclimate their jellyfish. It includes information about what water parameters the jellyfish should have.
- Nitrifying Bacteria Facts
Bio-Con Labs keeps a detailed explanation of how nitrifying bacteria function. Some of the information within is specific to a particular brand of cultured bacteria from Fritz-Zyme 9 by Fritz Aquatics.
- Chemistry and the Aquarium: Specific Gravity: Oh How Complicated!
This article by Randy Holmes-Farley gives an excellent and lengthy explanation of the relationship between salinity, specific gravity, and temperature, as well as some tips on how to gauge the accuracy and precision of your hydrometer.
- Low pH: Cause and Cures
This article by Randy Holmes-Farley gives an overview of pH in saltwater aquariums as well as how to diagnose and treat problems that cause out of range pH values.
- What is that precipitate in my reef aquarium?
This article by Randy Holmes-Farley explains what the precipitate in aquariums commonly is and how it forms.
Contact Information How to contact the author(s)
I was introduced to jellyfish by the cover of Wired magazine in late 2011, explaining how a company called Jellyfish Art would make keeping a jellyfish in the home as easy as taking care of a goldfish. This was, of course, patently false, but that didn't stop me from trying. After having fun doing a year of experimentation and research, I wrote this web-site to share what I found. I have started a coral reef tank, which I blog about, updating it with news about long-term coral health, new animals, or new tools and techniques to take care of the animals.