Guide to Keeping Jellyfish in Aquariums
Introduction
Keeping jellyfish is a relatively new trend in saltwater aquariums. Until recently jellyfish and jellyfish aquariums were not available. This guide is intended to share the knowledge of nearly two decades of research and development of our jellyfish tanks. Taken from our experience and collaboration with many colleagues over the years, we hope to inform you of the necessary facts to keep jellyfish. This guide pertains to tropical moon jellyfish and the methods used to care for them.
The Physical Environment
Jellyfish need round tanks because they get stuck in corners. Jellyfish also rely on water current to keep them suspended in the aquarium. Not all round tanks are created equal. We began our research with upright tube type tanks. This type of aquarium is suitable for more mobile jellyfish, like spotted lagoon jellyfish, but not moon jellyfish. Moon jellyfish do best in a kreisel type of aquarium. This design is like a tube turned on its side. Our aquariums are a pseudo kreisel meaning they use the surface of the water as a barrier to keep the jellyfish in the viewing area. We created this design because it provides easy access to feed and maintain your jellies.
Another important factor to keep jellyfish successfully is the size of the aquarium. It takes longer for a large volume of water to change than it does for a small volume. Stability is the key to successfully keeping any type of aquarium. You may have seen “desktop” jellyfish aquariums. These aquariums lack adequate filtration and necessary volume to keep jellyfish. Our jellyfish aquarium is large enough to be stable, but small enough to be manageable and includes necessary filtration.
The Chemical Environment
Water chemistry is important no matter what kind of aquarium you are keeping. Keeping jellyfish is no different. Jellyfish need a good quality salt like a reef tank does. A reef salt should have a good alkalinity of 9 DKh, a calcium level of 400-450 ppm and a magnesium level of 1280-1320. We recommend three aquarium salts: Omega Sea reef salt, Tropic Marin reef salt, ESV salt. All three salts will mix to the above chemistry at a salinity of 1.022-1.023, which is what we recommend. When setting up a jellyfish tank, one should use reverse osmosis/ deionized water. Replenishing trace elements to the aquarium is also important. Trace elements are depleted through normal biological process and/or removed though chemical filtration and protein skimming. Calcium and magnesium are especially important to jellyfish. Alkalinity stabilizes Ph, but Magnesium stabilizes alkalinity. Magnesium is also responsible for regulating metabolic process in all living organisms. Good magnesium levels are the foundation for any successful saltwater aquarium. Regular water changes are necessary to replenish major, minor and trace elements. Alkalinity may be the most important parameter in water chemistry. It is the first thing we test when experiencing difficulties. We recommend the ESV brand of supplements. The A&B bionic system for calcium and alkalinity maintenance and the magnesium supplement. These supplements are very high quality and in a liquid form. We also use and recommend the transition elements for minor trace element replenishment.
The Biological Environment
Jellyfish need clean water. Effective, efficient filtration is crucial for keeping jellyfish. Ammonia is extremely harmful to jellyfish as it can cause holes in the bell. Good biological filtration is a must. Aquatic organisms produce waste in the form of urea or dissolved organic compounds. This waste is transformed in the water column to ammonia. Aerobic bacteria that live on a surface area or bio media “eat” the ammonia as the water passes through it. The ammonia is converted to a second more toxic form of nitrogen called nitrite. A second strain of aerobic bacterial “eat” the nitrites and convert it to the more stable and less toxic form of nitrogen called nitrate. Strong aeration is necessary for an efficient biological filter. Our system aerates the water as it passes through the protein skimmer and the water goes directly to the bio media so the bacteria have plenty of oxygen to do their job. Nitrates are reduced through water changes, but can also be reduced by a process known as carbon dosing. Carbon dosing is an advanced technique that requires a protein skimmer. Our built-in protein skimmer makes carbon dosing possible. Essentially, some form of carbon is introduced to the aquarium that feeds bacteria in the water column that “eat” nitrates and convert them to elemental nitrogen. Care should be exercised when carbon dosing; the bacteria consume a great deal of oxygen that the bacteria in the bio media need to break down ammonia and nitrites. Water changes are still necessary to replenish major and minor trace elements and reduce dissolved organic compounds.
Feeding Jellyfish
Jellyfish will eat a wide variety of food as long as it’s small enough. Jellies eat a lot—in the ocean they are eating all the time. We typically feed twice a day. Dry foods are easy to use and can be very nutritious. We recommend the size A, TDO from Reef Nutrition for dry food. However, frozen/refrigerated foods work the best as moisture content aids in digestion. A staple food for moon jellyfish is frozen or live baby brine shrimp. We feed frozen baby brine shrimp daily. Another food from Reef Nutrition is R.O.E or real ocean eggs. These fish eggs are nutritious and the right size for jellies. Oyster eggs are another nutritious food for jellyfish. We have found that these smaller foods work well for small jellyfish that are 2-3 inches in bell diameter. When jellyfish hit 3 inches in bell diameter, they will need something more nutritious, with higher protein levels. We put frozen Plankton in a food processor and puree’ it.
When it comes to actually introducing food into the tank, the first step is to put the food into a small container to thaw it or hydrate it in aquarium water. After about five minutes, it’s ready to put in the tank. Food should be added so that it stays in the center of the viewing area. In our tanks, you pour it just to the left of center so the current keeps it suspended. The jellyfish should consume all the food in about 10 minutes. If most of the food is gone in five minutes, use more next time. If there is still food after 10 minutes, feed less next time. Jellyfish grow in relation to food , so if your jellies aren’t growing they probably need more food. If they are growing rapidly you could probably feed less.
Lighting
Moon jellyfish are non photosynthetic organisms, so one would think they don’t really need light. Color changing LED’s are very popular in moon jellyfish tanks. You see these RGB LED lights on the “desktop” jellyfish tanks and even in public aquarium displays. Something to keep in mind is that red LEDs are used in algae scrubbers to grow algae that consume nitrates and phosphates in advanced aquariums. Not really the kind of thing you want on a display tank. Second and more importantly, there are non photosynthetic needs for light. Remember how we discussed the importance of calcium and magnesium? These minerals are only useful if they can be absorbed. Recent research has indicated that plankton need UV rays to produce vitamin D, which is necessary for absorption of calcium and magnesium. Jellyfish are considered macro plankton or large planktonic organisms.
Temperature
Tropical moon jellyfish require water temps in the 70s. There are roughly 14 species of moon jellyfish, some require cold water others like warmer water. We sell only tropical moon jellyfish that don’t require a chiller. It’s important to note that temperatures over 80 degrees are deadly to jellyfish. It’s not really the temperature itself that is the issue. It is the water’s ability to hold gases; oxygen levels crash at temperatures over 80 degrees. We have found temperatures of 73-75 degrees are ideal. Cooler is better than warmer, but temps of 70-78 degrees are acceptable.
Handling Jellyfish
Moon jellyfish don’t have a detectable sting for human beings. You can touch one with no ill effects. When moving jellyfish around one should use a catch cup. These are often used in your local fish store for holding the bags they are putting fish into. You can use any plastic container large enough to fit the jellyfish. Just be sure to dedicate that container for aquarium use only and don’t use any soap to clean it. We typically use a two gallon bucket from the paint department at your local big box hardware store to hold and acclimate jellies. When you clean your tank you will need to remove the jellies and put them in the bucket. First, fill the bucket halfway with aquarium water. Then as the jellies drift past the top, scoop them up and put them in the bucket. This process takes just a few minutes and is necessary so you don’t injure them during cleaning or suck one up during the water change. You can leave jellies in the tank if you’re using a cleaning magnet to gently clean the glass, but if you’re using a cleaning brush you will need to take them out. Just remember these are not fish that you have to chase around to catch. Jellyfish are non the wiser to being moved around.