How on earth do you keep jellyfish at home?
Jellyfish are uncommon in the aquarium hobby, largely due to the fact that there is so little information on how to keep them. They are extemely unique and interesting creatures and are actually not that hard to keep. They are easier (and cheaper!) than most marine aquarium setups and about on par with a planted freshwater setup. Despite this, they do need some specific care conditions to allow them to thrive.
A crash course on Jellyfish biology
A crash course on Jellyfish biology
Jellyfish are extremely unique creatures, and while they are considered to be animals, they often share many similarities with plants. Jellyfish have between 4-6 stages of life, depending on which biologist you ask. Simplified, the stages of life are; Larvae, Polyp, Strobila and Medusa. When we keep Jellyfish, we generally speak of keeping Medusa, a fully grown adult jellyfish. Although it is the final stage of life, it is the longest lasting months to years. In the wild, Jellyfish Medusa drift around in the ocean currents and have little power to direct where they are going. Not that they’d want to in the first place, as they not have any brains to decide where to go! They are filter feeders, meaning that anything caught in their stingers gets transported to the jelly and is then digested. Because of this, they eat very small creatures that exist in the ocean, such as microscopic Zooplankton.
Tank setup
One of the defining parts of keeping Jellyfish is the tank they live in. They cannot thrive in the classic cube or cuboid shaped aquariums that you might be used to with other underwater creatures. Jellyfish are not very good swimmers as mentioned so they need a special shaped tank to house them without them getting caught in the corners of a traditional tank. These tanks are called Kriesel tanks (Kriesel being German for circle). They also allow you to keep a current going in the tank to keep the jellies suspended and moving without pumping air bubbles into the tank, which could be potentially fatal if they get caught under a jellies bell.
Many of the similar filtration requirements apply with jellyfish too, while jellies don’t produce a large amount of bioload (most of it stems from uneaten food), cycled filter media is required to avoid ammonia or nitrite build up. Our all in one kits come with biological bacteria that will help kick start the cycle in your tank but you can also use some aged filter media from your local marine fish store or a friend with a reef tank. You will have to perform water changes regularly to keep the nitrate levels down, but you can avoid this by keeping some marine macroalgae in your refugium/sump to soak some of that up. As jellyfish need pretty bare tanks, uneaten food may collect at the bottom of the kriesel tanks. While this is not damaging, it can get a little unsightly and we recommend you remove that whenever the build up gets too bad. You can do this either with a standard siphon hose or a turkey baster if you don’t want to risk sucking up and damaging your jellies.
A Kriesel tank suitable for housing moon jellies
What and how do I feed my jellyfish?
Jellyfish feeding is a bit more involved than most other aquatic animals. Jellyfish also aren’t very complex animals, they regulate their growth based on how much food they in take. When you feed jellyfish there are two main goals you can have in mind.
Feeding to Grow
While this is generally more applicable to breeders, feeding to grow is also viable when you you’ve bought smaller jellies that you want to increase in size to fit the aquarium, or if you have recently increased the size of the tank youre keeping your jellies in. When you feed to grow you are feeding with the intention of your jellyfish to put on size, the best way to do this is to feed your jellies live baby brine shrimp (gut loaded is even better, if you can). If live bbs is not available to you, feeding with coral food (such as reefroyds, Coralific delight or SPS coral food) is also an alternative. For both feeding methods it is important to note that not all food will be eaten by the jellies so any food that falls to the floor of the tank needs to be kept clean and removed. It is also best to feed twice a day, once in the morning and once in the evening, to maximise growth in your jellies.
Feeding to maintain size
Feeding to maintain size is the most important for the average jellyfish keeper. This involved feeding the jellyfish to allow it to grow slowly and steadily, thus staying generally the same size. This method also allows you to keep jellyfish in smaller tanks without hurting or stressing the jellyfish. The best way to do this is to feed a smaller amount of food to your jellyfish. In our limited testing we have found that hard-boiled egg yolk dissolved in tank water seems to be an easy way to keep the jellyfish growing very slowly. Dissolved egg yolk also has the advantage of being extremely small in size, thus not settling on the tank floor and causing much less of a mess. Egg yolk can be a little bit difficult to store however, and would not be suitable to drip or auto-dosing feeding systems. If thats the case, coral foods or fry foods such as Sera Micron or Hikari First-bites are also a good solution that are easier to store and feed.