Jellyfish Feeding Problems & Solutions | TFH Magazine

Issue: December 2009

what to feed jellyfish

Feeding Jellyfish: Problems and Solutions

Author: Jim Stime, Jr.

Creating a proper setup for jellyfish is only one of the challenges in keeping these increasingly popular marine specimens. A jellyfish expert describes his latest triumph in caring for jellies—a feeding program that provides enough of the right nutrition without adversely affecting the environment of these beautiful but sensitive creatures.

The New Frontier

It’s interesting how life (or more specifically, in my case, the process of product development) can present certain awakenings or realizations. I have spent the last five years learning how to produce jellyfish and developing systems for holding them, and during that time my realizations have ranged from grasping a simpler method of accomplishing laminar water-flow distribution to visually experiencing the separation of an ephyra from a polyp. I would like to share with you my most recent epiphany, the significant advantage of hatching and decapsulating brine shrimp cysts and their use as a food for moon jellyfish.

Jellyfish are the new frontier of the marine aquarium hobby, and hobbyists can get in on it fairly easily. There are a few good articles detailing the reproduction processes that have already been mapped out, as well as the availability of new technologies in production and display tanks. But with all these advancements, feeding jellies remained a bit of an unknown—until now. Move over, Emeril, it’s jellyfish-food cooking time!

How Jellyfish Eat

Jellyfish, specifically moon jellyfish Aurelia aurita, swim through the water column and simply bump into their food. They may have primitive optical eye spots, but these can only be used to determine light and dark. In order to perceive something, they must bump into it. My point is that their food needs to be in the water column where they are. Jellies do not feed or forage off the seafloor or the bottom of the jellyfish tank.

Beautiful and hypnotizing, they pulse through the water with trailing ribbons of frilly lace and fringe, and that pulsing motion is the means by which moon jellies collect their food after they have bumped into it. The slimy coating over the bell of the jelly holds onto these food particles, and as the bell pulses, these food items are moved to the outer edge of the bell. Along the rim of the bell are fringe tentacles that grasp the food items and whip them around, passing them to the four trailing oral arms. These arms extend downward from the underside of the jellyfish and pull the food items back up and into its stomach, which, in the case of the moon jellyfish, resembles a four-leaf clover on the top side of the bell.

Food Problems

Let me back up a couple of steps, though. Until recently, I thought that the advantages of the nutritionally engineered and commercially available frozen aquarium plankton foods outweighed the time and effort to prepare live foods. For all of the conveniences of frozen foods, however, they really are not that good of a choice in the jellyfish tank, the reason being that within a few rotations of the water within the tank, gravity wins out, and the food begins to settle onto the bottom of the tank.

This settled debris causes a few problems; it not only looks bad but requires you to go into the tank often to siphon it out, which you really want to minimize because jellies are as delicate as wet tissue paper and can be damaged or torn quite easily. Additionally, the longer the debris remains in the tank, the worse it is for the jellies’ environment because it allows the development of various fouling organisms.

Baby Brine Shrimp

I have found that live foods such as freshly hatched baby brine shrimp (Artemia nauplii) are of a very appropriate size for jellyfish polyps, ephyrae, and juvenile jellies. They are also very nutritious if fed right after hatching. The biggest advantage is that they are alive and continue to swim within the water column where the jellies can continue to feed upon them, rather than settling at the bottom of the tank as do non-living foods.

I started with a simple 12-inch-tall, cone-shaped brine shrimp hatchery and an air pump. I was successful in doing so, but all I was doing was hatching—I was not separating the shrimps from their shells and, in turn, as much as 50 percent of what I thought was live food turned out to be the shells of hatched brine shrimp and unhatched eggs. There was no real decrease in debris at all. As a matter of fact, I now had debris on the bottom of the tank as well as the surface. Worse yet, all those shells were of no nutritional value, and in fact were actually problematic if consumed by the jellyfish, as they could actually rot their way through their bells and stomachs.

I once again had a bad environment for the jellies developing in my tanks. Worse, it seemed to harbor what I incorrectly assumed was some sort of bacteria or protozoan that would actually attack the jellyfish and begin to eat holes through their bells, something I called the “Swiss Cheese Syndrome.” It got so bad that healthy adult jellies that entered my system and then went into another system carried the problem with them.

Finding Solutions

After much frustration, I decided to call upon a friend, Justin Pierce of Medusa Labs, who had helped me way back in my jelly-beginnings five years earlier. Justin flew out and, within a short period of time, determined that I had two issues. The first was that I needed to remove the shells of the brine shrimp before feeding them to the jellyfish. Not only were the shells of no nutritional value, but the jellies couldn’t digest them either, which may have caused the holes in the bells of the jellyfish. His second comment was that my tanks had too much debris in them, which created a bad environment.

Another jelly-head friend of mine, Chad Widmer of the Monterey Bay Aquarium, described this environment as “both mechanically abrasive to jellies and [allowing] a menagerie of microscopic fouling organisms a place to thrive.”

My Experiment

Ugh, who wants to go through the decapsulation process? Still resisting, I had an opportunity to try an experiment. There was a local weekend hobby trade show here in southern California. I had planned to set up a large jellyfish tank display and had made arrangements to bring in some imported Japanese moon jellyfish. While expensive, a dozen 6-inch-diameter jellies make for a very impressive display. I made it a point not to place these jellies in my system and instead held them in their original shipping bag, which I floated in another operating system for two days. I would open up the bag every few hours and allow some of the system water to enter the bag of jellies.

These jellies went to the show, displayed awesomely, and then after three days came back home. I again held them in their bag for another day until I could set up that same display tank. I used new salt water and brought that temperature down to 60°F. After a few more hours, I acclimated the bagged Japanese jellies and released them into this newly set-up tank. They remained there for four more weeks before I ended up selling them to a service company in New York City.

I will tell you that between the time I received them, displayed them at the show, and held them another four weeks afterward, I did lose two of them. But during this time, none of these jellies showed any signs of the Swiss Cheese Syndrome.

Decapsulation Method

At this point I was convinced that the problem was in my system. Based on Justin’s suggestion, I needed to increase the cleanliness of my tanks and decapsulate the brine shrimp cysts. I started by completely cleaning and sterilizing my entire breeding system to rid myself of this current plague. I also needed to develop a method or process for decapsulating the brine shrimp cysts.

It was right about this time that the light bulb came on. It occurred to me that the majority of the debris in the tanks was either hatched brine shrimp shells floating at the surface, or unhatched shells and jellyfish waste that had settled at the bottom of the tanks. “Gosh, if I was just able to eliminate the shells from going into the tank, this would eliminate the shells floating at the surface and a large portion of debris from collecting at the bottom of the tanks.” This one step could eliminate two problems!

Removing Shells

There are two basic methods for removing the shells from the Artemia cysts. Prior to hatching, one has to dissolve away the outer shell using chemicals (bleach, specifically) or, after hatching occurs, use natural buoyancy as the means of separation. Both have their positives and negatives.

Method 1

If going the chemical route, removal of the shell can only be performed when the cysts are fully hydrated. Full hydration can only be reached by soaking the cysts in warm fresh water for about two hours. It’s recommended to stir the cysts during this time to ensure that an even hydration occurs among all the cysts. Drain that water and immediately place the hydrated cysts into salt water. Now add 3 to 5 percent sodium hypochlorite solution (bleach). Stir the brine shrimp eggs thoroughly for 5 seconds every 30 seconds, for approximately 10 minutes. Oh, my arm already hurts...

If you search the Web for “brine shrimp decapsulation,” you will find a few variations on this bleach-soaking time frame—from 5 to 13 minutes. Did I mention that you have to stir the cysts constantly during this phase? It may be better to base the time frame on a color change. The chemical reaction of dissolving the shell causes heat. The stirring helps dissipate the heat that would otherwise cook the shrimp.

The cysts will change color from brown to white to orange. The brown is the tough, wet outer shell, and the silver or white is the shell reacting to the bleach. The orange color is the bare shrimp egg; its shell has now dissolved away. As soon as the cysts become orange, drain the liquid and immediately rinse with fresh water. It may require the use of substantial amounts of sodium thiosulphate (dechlorinator). Drain and repeat until there is no more chlorine smell, and then rinse with straight fresh water again. You now have shell-less shrimps, but they still need to be hatched.

Method 2

The alternative is post-hatch separation and natural buoyancy. Using a tall, tapered vessel with heavy aeration, one allows the brine shrimp to hatch from their shells over a 24- to 48-hour period.

After that time, the aeration is discontinued for about 5 to 10 minutes. A distinct separation will occur as the water movement stops; the hatched eggshells will float to the surface and the unhatched eggs will sink to the bottom.

Most of the newly hatched brine shrimp (nauplii) will accumulate just above the unhatched cysts, down near the bottom.

At this point, one can siphon the shrimp out of the hatchery using a length of airline tubing with a rigid extension on the intake end, allowing one to position and very accurately siphon out just the freshly hatched brine shrimp. The method I use is very similar, only that I drain the water through the bottom from the tapered vessel with the use of a bottom-placed gate valve.

The first order of business is to draw off the unhatched cysts. After discarding those stinky, unhatched cysts, I resume draining the hatchery, this time drawing out the shell-less newly hatched shrimps. As the water level in the hatchery drops down, the empty shells that collected at the surface begin to collect on the inside of the slowly restricting tapered panels.

It’s like a natural separator. Once I have drained out all the visible shrimps into another container, I then lift out the entire hatchery to pour out the debris, the balance of the shells, and then rinse out the inside of the vessel and prepare it for the next hatch.


Now that I go through the decapsulation process and am feeding just live baby brine shrimp, I have noticed a significant decrease in debris collecting on the tank bottoms. In fact, just now as the jellies are getting an inch to 2 inches in diameter (that’s 60 days old), not only is there truly minimal debris collecting in the tanks, but I have not seen a sign of Swiss Cheese Syndrome. Additionally, I have gone from a frustrating 5 to 10 percent growth to a saleable 2-inch size, to around 60 to 70 percent success in growing tank-raised moon jellyfish.

The point of my story is not to impress you with my ability to decapsulate brine shrimp cysts, but to show the direct result of my doing so: the significant, night-and-day improvement in the number of animals I am able to raise. An additional benefit is the noticeable decrease in debris collecting in the tanks, leading to less intrusion needed on my part to clean the tanks and potentially suck up or damage juvenile jellies. The bottom line is that I am able to successfully grow more jellies for this growing “frontier” market in the aquarium hobby.

See the full article on TFH Digital http://www.tfhdigital.com/tfh/200912/#pg93

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