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 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 is welcome and appreciated. This guide was last updated on August 3rd, 2014.




Tip: Green colored boxes are good habits I found helpful in ensuring my jellies stayed healthy.
Upgrade: Blue colored boxes are tests or modifications I perform to ensure that the aquarium and the environment is healthy.
Caution: Yellow colored boxes are cautionary warnings about things that are harmful to your animals.
Important: Red colored boxes are strong warnings about things that may kill your animals.
Jellyfish require excellent water quality to thrive1, it is highly advisable to buy a saltwater testing kit (not freshwater) to test the tank water. I enjoy using the API (Aquarium Pharmaceuticals Inc) brand due to the quality glassware and bright colors, but Salifert, Elos, and Red Sea are also reputable. The API kit is available on Amazon here. You should have your tank water fall within the following ranges presented in the accompanying table.2, 3, 7

Test: If you are not confident in your testing kit, try testing your freshly mixed saltwater at least once. This lets you see what a 0.0 ppm reading for ammonia actually looks like. It also is a good way to ensure that your salt and water sources are free of nitrates (NO3-) and ammonia (NH3). You can also buy a second testing kit (possibly from a different brand, and compare the results).

API Saltwater Testing Kit on Amazon
Caution: Your jellyfish can survive for many days in levels of ammonia (NH3), and nitrate (NO3-) that are much higher than ideal, but the long-term health effects are believed to include shortening tentacles, weaker pulsing, and a flattened bell. If left in poor water for months, these conditions will eventually lead to jellyfish mortality.3
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 that high 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.

Tip: Jellyfish are sensitive to changes in salinity, temperature, and pH.5 Try to keep their environment as stable as possible, especially when cleaning the tank and changing their water. Let the replacement water reach the same temperature as the tank, let it air out, and check the salinity carefully.
Parameter Ideal Range2, 3, 7
pH 8.0 - 8.3
Salinity 32 - 34 ppt
Ammonia (NH3) 0.0 ppm
Nitrite (NO2-) 0.0 ppm
Nitrate (NO3-) 0.0 - 20.0 ppm
Test: Swing-arm hydrometers (such as the one provided by Jellyfish Art) are temperature sensitive.9 The one that comes with the tank is set for sample taking at 25°C or 77°F. Most house's ambient temperatures are lower, and lower temperatures affect both the hydrometer material density as well as the water sample density. There is also no indication of what temperature standard is used for the markings provided on the hydrometer. If your house temperature is making the salinity readings difficult, buy a refractometer that compensates for temperature.

BRS Refractometer on Bulk Reef Supply
Water used for your jellyfish tank should preferably be steam distilled or passed through a reverse osmosis and deionization process; watch out for water that says reverse osmosis but includes minerals for taste. Do not use tap water, this is to prevent the possible introduction of chlorine (or chloramines) that will harm your animals, as well as prevent the concentration of metals or other contaminants building up in the tank due to evaporation.

Caution: Ensure that all items going into your tank are rinsed with distilled water only, and not with tap water. If your tap water is heavily treated, the chlorine will hinder the nitrogen cycle in your tank.
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 weekly water changes. 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. You will need to change water in your tank more frequently if you have extra animals in the tank.

Important: Although Jellyfish Art claims their cleaner snails will eat uneaten food, all the snails I have received do not. The picture and description on their website is of Nassarius Vibex, but the snails I received were Cerithum, which eats only algae.
Tip: Mix your salt water a day in advance and let it air out or use a powerhead pump in a bucket. This allows the water to reach its carbon dioxide, oxygen, and pH equillibriums.10 Try to have your replacement water match the salinity, pH, and temperature of the tank before doing a water change to minimize stress on your animals.
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 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.

Caution: Avoid changing more than half the tank water at once if you can. While it will reduce the concentrations of ammonia (NH3), etc., it has a higher risk of shocking the jellies due to a difference in salinity, pH or temperature. In addition, any changes will delay your nitrifying bacteria from "working" and reproducing as they adjust.8 If you are consistent in how you mix your saltwater, and the salinity, pH, and temperature match the tank, this is not a danger.
Tip: When mixing your salt water, it is a good habit to add the salt to the total volume of water you desire; not pour water onto your salt.11 This will prevent the initial small amount of water having a large amount of salt dissolved in it, combined with a high pH, thus causing precipitation of minerals.11 This precipitate is harmless with regards to jellyfish, do not be alarmed if you see it in your tank or mixing containers.
Important: Do not adjust your salinity by putting salt crystals or concentrated salt water into your tank. This can kill 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

Caution: Do not change the water unless necessary for the first 4 weeks. Each time you do, the nitrifying bacteria may take time to adjust. Minimize feeding for this first month. This will allow the nitrifying bacteria time to establish themselves without generating an excessive amount of ammonia in the tank.2
If you have removed more bacteria than you'd like, you may purchase a bottle of Fritz Zyme 9, 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.

Upgrade: You can buy Instant Ocean BIO-Spira and other nitrifying bacteria supplements on Amazon.

8.45oz Instant Ocean BIO-Spira on Amazon
In the wild, jellyfish will normally have their prey bump into their tentacles and oral arms.1 The prey is stung by nematocysts on the thin hair like tentacles on the edge of the bell as well as the oral arms.1 The stung prey is quickly dragged to the edge of the bell and the jelly's pulsing movement tranfers the prey to the four large oral arms in center of the bell.1, 5 As the oral arms retract, prey is moved up into the mouth and then into the four stomachs.1, 5 It is uncommon but not extremely rare to find mutant specimans with five or more stomachs. This has no effect on the jellyfish's ability to capture and digest prey.

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

Tip: Ensure that the container used to mix the food is clean. Dirty containers can establish large bacteria colonies that transfer into your tank, possibly harming your jelly. With some bad luck a saltwater strain will cultivate in the container and eat holes in the jelly.2 In extreme cases, the jelly may totally disintegrate within 48 hours.3
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.

Caution: Do not squirt food directly at the jellyfish, despite what the instructions from Jellyfish Art state. In the long-term, this will disrupt the natural interaction of how its nematocyst stinging cells help stimulate the jelly's swimming.2
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 (or have recommendations).
Upgrade: If your pH is too high, you may add a small ¼ cup of marine sand into your tank to lower the pH. Any sand acceptable for reef keeping will do, avoid sands that are not intended for aquatic purposes as they have a different chemical composition and will not lower the pH, in addition to introducing unwanted elements into your tank (e.g. metals, etc.). I bought this sand, but there are many others that are also appropriate (and come in smaller quantities).

CaribSea AragAlive 20lbs reef sand, Fiji Pink
Tip: While not strictly necessary, hatching live baby brine shrimp is a helpful way to ensure your jelly gets proper nutrition. Live food is an easier way to ensure the jelly gets its food without excessive cleanup. However, the process is labor intensive, so it is matter of tradeoff, whether you prefer cleaning or breeding. See the baby brine shrimp enrichment guide on this site.
Jellyfish require a gentle current to maintain their shape and their health.1 Your jellyfish should have enough current to be lifted off the bottom of the tank if they sink. Owners of the Jellyfish Art tank will want to reduce the current enough that the jellies will not become scratched from brushing against the substrate. The owners of the EON and Cubic tanks do not need to worry about this.

Upgrade: If you did not receive an air valve with your jelly order, you can adjust your air pump by tying a loose knot in the air hose leading into the tank. Alternatively, you can buy a 2-way air valve from any fish store and cut your air hose in half and install the valve to connect the two pieces (verify width first!). Give the tank at least 10 minutes to allow the full current change to occur before making further adjustments.1
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 a 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.

Caution: The greatest danger to your jelly is still poor water quality; without excellent water quality your jellyfish will have greater difficulty healing, and may permanently evert. Jelly eversion can become permanent and kill your jelly by preventing it from feeding.
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, Nutrafin 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.

Tip: Owners of a Jellyfish Art tank can use the following steps to rescue a jelly from the substrate without harm:

  1. Turn off your air pump to avoid having the jellyfish sucked through the air channel while you rescue them.
  2. 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)
  3. 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.
  4. 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
Jellyfish that are stuck in the substrate for several hours (e.g. overnight) will flatten or stretch out and have difficulty moving for around a day while they recover. A jelly stuck in the substrate for a shorter amount of time may take only minutes before it begins to swim normally.
Tip: If your jelly gets stuck in the substrate, turn your water pump off for a short while until you are sure it has regained the ability to swim. Depending on how long the jelly was stuck, it will take several minutes to a day for it to regain its shape and swim normally. Your pump can remain off for up to 4 hours before it will slowly drip water from the escape valve.
Tip: Gently swirl the water with the feeding pipette to give the jelly some current while your air pump is off.
If your jellyfish is beginning to flip inside out (e.g. jellyfish eversion syndrome), there are several potential causes:1, 3

  1. Dramatic salinity change
  2. Dramatic temperature change
  3. Poor water quality (ammonia, nitrites, nitrates)
  4. Lack of proper nutrition (diet is lacking nutrients, or food not getting into stomachs)
Check each cause and adjust as appropriate; some will only happen during water changes. In good health your jellyfish should be pulsing about once every 1-3 seconds at room temperature and each pulse should provide enough locomotion to escape suction at the bottom of the tank and maneuver in and out of the center of the tank.

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

Upgrade: If you own a Jellyfish Art desktop tank, it is highly recommended you replace the substrate provided with something smaller but porous. I have been using CaribSea coarse calcium reactor media, but there are many other options available.

8lbs CaribSea ARM coarse on Marine Depot

Tanks

Jellyfish Art

Moon Jellyfish

Cubic Aquarium

Jellyfish Art sells a kreisel desktop tank that uses a covered air channel to generate the laminar flow that keeps the jellyfish suspended. A light-weight porous substrate covers the bottom of the air channel, preventing the jellyfish from being sucked into the air channel while also acting as a biological filter housing the nitrifying bacteria.

Every tank comes with everything needed to get up and running, and even includes accessories for total beginners (a feeding pipette, and a swing-arm hydrometer). Deluxe editions of the tank include vouchers for live animals, as well as additional equipment, such as a cleaning magnet, water testing kit, bacteria seeding supplment, and extra substrate.
The EON jellyfish tank is a miniaturized version of several larger tanks developed by Moon Jellyfish, the newly established retail branch of Sunset Marine Labs. With 16 years of experience, Sunset Marine Labs has supplied jellies and tanks to aquariums, restaurants, and homes throughout the world. The tank generates its gyre flow through two spray bars in the tank that generate a circular flow keeping the jellies suspended in the tank.

The tank has an integrated filtration system that includes mechanical (a gauze filter), biological (media with nitrifying bacteria), and chemical filtration (activated carbon bags). In addition, the EON tank comes with three 2" jellyfish and 80g of food with the purchase of a jelly.
Cubic Aquarium released the Orbit 20, a new kreisel desktop tank in May 2014. While similar in appearance to the Jellyfish Art tank, the Cubic Orbit 20 has a few features above the Jellyfish Art tank at a slightly higher price. Notably, these include a mechanical filtration feature, and no substrate (which makes cleaning easier). While costing slightly over $100 compared to the Jellyfish Art tank, the added convenience in cleaning and higher build quality can be worth it.

Cubic Aquariums also makes the Pulse 80 and Pulse 280 jellyfish aquariums, which are approximately 20 and 70 gallons each. Distribution of all three of these tanks changes rapidly as the Cubic Aquariums is European and is still building its relationships with US retailers. Check with the Cubic Aquariums website for links and references for finding one.
Item Cost
Jellyfish Art desktop Tank $285.00
Item Cost
EON Jellyfish System $850.00
Item Cost
Cubic Orbit 20 Tank $389.00
Pros:
  • Tank is significantly cheaper and includes useful starter equipment for those who have none.
  • Tank can be used as is to hold fish or a pico-reef.
Cons:
  • Substrate provided with tank can trap jelly oral arms, leading to damage. Changing out the substrate is highly recommended for the long-term health of jellies.
  • Substrate traps food particles making cleaning the tank inconvenient. Jellies will need to be removed to safety before substrate can be cleaned.
  • Lack of carbon or mechanical filters makes water changes time consuming.
  • Current must be fine tuned to give enough flow for jelly long-term health without dangerous suction into substrate.
  • Acrylic scratches easily, even with algae magnets that are meant for acrylic tanks.
Bottom line: The Jellyfish Art desktop tank requires care and effort to maintain water quality, but is the most affordable tank. It is suited both towards experienced reefers who already have an established tank they can exchange tank water with, or beginners who have the time and energy to change the water. It is also vital that the substrate be replaced with something smaller but still porous (such as CaribSea coarse calcium reactor media), and the current be adjusted down appropriately.
Pros:
  • Tank filtration system minimizes maintainence necessary to keep water clean.
  • Substrateless bottom means jellies cannot be scratched or torn on substrate.
  • Food stays suspended longer, minimizing waste.
  • Excellent customer support combined with nearly two decades of experience raising moon jellies.
Cons:
  • Cannot use any substrates in tank for decoration due to presence of LED lights in bottom panel.
Bototm line: The EON Jellyfish System is an excellent overall system that has a well thought out design that reflects the company's long history and experience with moon jellies. Combined with the company's excellent customer support, the tank is a great product for anyone who is interested in having a unique and amazing household decoration/pet. Although more expensive than other options, the tank will give a great experience provided it is cared for properly and the directions followed.
Pros:
  • Tank is still cheap and close in cost to the Jellyfish Art tank, but has higher build quality and more useful features.
Cons:
  • Some care should be taken while changing tank water as there is no sump or separate compartment.
Bottom line: The Orbit 20 is a great tank for those who want less maintainence but don't want to buy one of the more expensive and larger tanks. The Orbit 20 is also good for owners who are not yet ready to invest in more expensive tanks, but want a quality product.


Jellyfish Suppliers

Company Sizes Available Comments
Moon Jellyfish / Sunset Marine Labs Small (2"), Large (3") Sunset Marine Labs has 16 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.
PB'N'Jellies Small (1"), Medium (2"-3"), Large (3+") PB'N'Jellies is owned by Wyatt Patry, a senior aquarist at the Monterey Bay Aquarium responsible for the jellyfish exhibits. Wyatt Patry recently made a breakthrough at breeding Crown jellyfish in captivity. PB'N'Jellies is Wyatt's business selling moon jellies, in addition to an aquarist blog that he maintains.
Jellyfish Art Small (1.5"), Large (3") Jellyfish Art is a 2 year old company that is based out of San Francisco. 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.
Think Jellyfish Medium (2"-3") Think Jellyfish is a brand new company started by Travis Brandwood and Zane Smith. They have been developing a captive bred moon jellyfish population and have just begun to offer them for sale.
  1. 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.
  2. Nancy Sowinski
    Nancy is the owner of Sunset Marine Labs, and their retail division Moon Jellyfish. With 16 years of experience, she has provided moon jellyfish to a variety of aquariums, restaurants, and clubs world wide.
  3. 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.
  4. PB'N'Jellies
    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.
  5. 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.
  6. Aurelia Aurita
    Wikipedia article on Aurelia aurita, also commonly known as the Moon jellyfish.
  7. 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.
  8. 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 FritzZyme 9 by Fritz Aquatics.
  9. 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.
  10. 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.
  11. 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.
Jonathan Hsu

Jonathan Hsu

Jonathan has no prior experience with jellyfish, saltwater aquariums, or marine life in general. As an engineer, Jonathan is just happy to have a chance to figure things out, experiment, write down the results, and admire just how pretty animals can be.

Email Jonathan