Robert Toonen
Jellyfish
May 17, 1998 on #reefs

I'm sure that everyone here is familiar with some familiar members of the Phylum Cnidaria, such as hard and soft corals, gorgonians, sea pens and anemones.

However, the Cnidarians encompass a much broader range of body forms than these animals on which most reefkeepers focus.

This group also includes the hydroids (although these animals are incredibly diverse, they are rarely of interest to aquarists and are often known by such flattering names as "snail fur"), the sea lillies, the siphonophores (an odd group of jellyfish-like hydroids that most resemble a charm bracelet!), and half the focus of our discussion tonight, the jellyfish.

Why only half? Well, because I want to discuss all the gelatinous zooplankton people could potentially keep in their tanks, and that includes another Phylum, the Ctenophores (the "comb jellies" or "sea walnuts").

The reason that these animals get the common name "comb jellies" is that dozens to hundreds of tiny hair-like extensions called cilia are arranged into transverse bands to form eight "comb" rows (ctenes) running along the ctenophore's body.

The light reflecting off the tiny hairs forms a kaleidoscope of color any time the animal moves, and the tiny rainbows created by the motion of the ctenes is what most fascinates many people with these animals and makes them a desirable tank occupant. (there is a great display of these animals at many public institutions, such as the Monterey Bay Aquarium, and I highly recommend the trip -- especially if you've never seen live ctenophores or jellies!).

Some very old zoology textbooks and some recent aquarium books (e.g., Tetra's Manual of Marine Invertebrates) still try to lump Phylum Cnidaria together with Phylum Ctenophora into the artificial category Phylum Coelenterata.

Coelenterates were once thought related simply because jellyfish and ctenophores were both gelatinous planktonic animals, and being a Jello-like predator was deemed unique enough to warrant placing them into the same taxonomic group.

However the similarity between jellyfishes and ctenophores ends there. The body symmetry is different, the number of embryonic dermal layers is different, the specialized cells used to catch prey differ, the gut is far more complex in ctenophores, and the list goes on.

Even after it became obvious that jellyfishes and ctenophores were unlikely relatives, many researchers were convinced that ctenophores were simply a specialized form of jellyfish by the observation that a couple of ctenophores were found to possess nematocysts (the specialized stinging cells of cnidarians).

Finally, careful work with one of these species (Haeckelia) revealed that the ctenophore was incapable of producing the cells, but rather took unfired cells from their prey - the tentacles of a jellyfish (Aegina) - and used them for it's own defense.

I have discussed some of the biology and morphology of both jellies and ctenophores in an article for Aquarium.Net, and it is in the archives there if you are dying for more details on the specific biology of these groups (http://www.aquarium.net/1296/1296_8.sht).

Therefore, I won't spend a lot of time telling you how a comb jelly differs from a true jellyfish here, but before we get into a discussion of husbandry, I will spend a little time telling you what a jellyfish is. For the sake of brevity I will use the term "jellies" to refer collectively to the jellyfishes and the comb jellies in this talk.

If I want to refer specifically to one or the other group, I will use the full name, but in cases where I use the word "jelly" without any qualifier, you can assume that I either made a slip or am talking about both (with equal likelihood).

I want to start with this: I want to take a poll asking if the "Portuguse Man-Of-War" (Physalia) is a jellyfish?

Actually, I won't do that because I don't know how, but I will tell you that I'm pretty sure the majority of you would have voted "yes."

That is incorrect - it is not a jellyfish at all but a specialized hydrozoan (related to the fire corals) that resembles a jellyfish.

I could also trick you by showing you a JPG of a nondescript fuzz composed of tiny anemone-like polyps on the sides of a tank (Aurelia) and ask you if that was a jellyfish - I suspect the vast majority of you would answer "no," and would again be wrong.

Wait - something that looks like a jellyfish is not and something that looks nothing like a jellyfish is one? How can that be? So what exactly is a jellyfish, anyways?

WHAT IS A JELLYFISH?

To answer that I have to start at the beginning and tell you a little about the classification of cnidarians and how they reproduce.

The Phylum Cnidaria is divided into 4 Classes: Hydrozoa, Scyphozoa, Cubozoa and Anthozoa. Three of those classes (Hydrozoa, Scyphozoa and Cubozoa) include members that produce a "jellyfish" stage (or more correctly a medusa stage).

The Phylum Cnidaria is divided into 4 Classes: Hydrozoa, Scyphozoa, Cubozoa and Anthozoa. Three of those classes (Hydrozoa, Scyphozoa and Cubozoa) include members that produce a "jellyfish" stage (or more correctly a medusa stage).

The Scyphozoans are the true jellyfishes. The Cubozoans are also "true jellyfishes" but to differentiate them from the Scyphomedusae, these animals are called Cubomedusae.

The final class, the Anthozoans, include all the Cnidarians we typically see in the LFS: the hard and soft corals, the anemones, the gorgonians and sea pens, the zoanthids and corallimorpharians (mushrooms), as well as the less common tube anemones.

None of these animals produce a medusa.

OK, so what do I mean by "produce a jellyfish/medusa stage?"

Well, the three classes that produce pelagic medusae have what is called a "alternation of generations" (a form of complex life cycle common in plants as well).

In this life cycle there is an asexual stage (the polyps, which divide by fission, much like their cousins, the anemones) and a sexual stage (usually the medusa).

There are MANY variations on this basic theme (e.g., in some species of hydrozoans this sexual stage can be a specialized polypoid, in others it is the medusa -- in scyphozoans it is the medusa stage that is sexual), but in general the life cycle goes something like this:

ASEXUAL STAGE

planula larva -> metamorphoses into a polyp -> grows into a colony of polyps -> specialized polyps (gonozooids) develop that produce immature medusae -> immature medusae grow and become sexually mature.

SEXUAL STAGE

sexually mature medusae spawn and produce fertilized eggs -> egg develops into planula larva --> return to asexual stage.

Note: many hydrozoans do not have a medusa stage (e.g., Tubularia, Hydractinia), and as I said, there are MANY variations on this basic theme, but you get the idea.

Scyphozoans (the true jellyfishes) are a little different. Scyphozoans:

ASEXUAL STAGE

planula larva -> metamorphoses into a polyp (scyphistoma) -> scyphistoma buds many others -> as scyphistomae grow some begin to strobilate (cut themselves up horizontally like a stack of dinner plates, each of which will eventually develop into an immature medusae called an ephyra) -> ephryae grow into sexually mature adult medusa.

SEXUAL STAGE

sexually mature medusae spawn and produce fertilized eggs -> egg develops into planula larva --> return to asexual stage.

Note: many scyphozoans lack a polypoid stage, and fertilized eggs develop into a planula larva which metamorphoses directly into an ephrya (e.g., Pelagia), and again there are MANY variations on this basic theme.

In general among these species, the polyp form is either small and inconspicuous or, as I just mentioned, in some cases altogether absent.

In contrast to the tiny unobtrusive polyp, many of the medusae can be very large. For example, some tropical species have tentacles that exceed 60 feet from the top of the swimming bell to the tips of the tentacles!

Cubozoans:

Most aquarists will never have seen a Cubozoan, and if they ever come into contact with one, they will most likely never forget it.

They occur in all tropical seas, but are especially abundant in the Indo-West Pacific. These jellyfish all remain fairly small (about 15 to 25 cm tall), and are active predators, occasionally chasing down and capturing their prey in rapid swimming bursts.

They have earned the name sea wasps for good reason. Their sting is extremely painful, and in some extreme cases even potentially fatal to humans! For that reason they should not be considered for any typical home aquarium.

OK, so the simplest definition of a "jellyfish" is the sexual stage (medusa) of the life cycle of these three groups.

Thus, the Man-Of-War, which is a colony of specialized polyps, each developing to become a different part of the "body," may ultimately resemble, but is not a jellyfish. I hope that everyone follows that?

JELLY FEEDING

Let me start by debunking a couple of misconceptions about jellies.

First, contrary to popular belief, jellyfish and ctenophores do not simply extend their tentacles and hope that some unlucky plankton swim into them. These animals have species-specific shapes and "fishing" behaviors that lead to them specializing on one or a few prey types in the wild.

Second, jellyfish are highly prone to tank size and shape altering their ability to capture certain prey, although their specific fishing behaviors lead to nearly exclusive capture of certain prey in the wild.

I once did a series of experiments in which I showed that even tiny hydromedusae (~0.5 cm in diameter) were dramatically affected by the size of container in which they were kept.

In my experiments, I showed that the jellyfish on which I was working (Proboscidactyla, if anyone is curious) changed their diet from their natural preference of snail larvae to copepod or Artemia nauplii (which they never seem to eat in the wild) unless they were in a container that exceeded 10-15,000 times their body volume!

That means that for a 0.5cm diameter jellyfish, the size of aquarium needed to duplicate natural feeding behaviors is roughly 1 gallon. That doesn't sound bad, but this value scales up VERY quickly!

For example, studies on some Mangrove jellyfish from Palau (about 10-15 cm diameter) have found that these animals needs a minimum volume of about 650 gallons to survive long-term.

In the end, you may not really care, or need to reproduce natural feeding behaviors in the home, but you should be aware that many species of jellies do have specific prey and that they may never reach breeding condition unless provided with the appropriate diet.

Thus far, however, I have not had problems keeping alive any of the jellyfishes I have caught by feeding them on live brine shrimp (Artemia), at least for short periods of time. Selcon-enrichement of Artemia seems to speed growth and prolong life, as does a varied diet of live and in some cases even frozen foods.

JELLIES IN THE HOME AQUARIUM

So I guess this is the real meat of the talk. After all, the biology is sorta interesting to some people, but the bottom line everyone generally wants to know is "How do I set up a tank like that in MY living room?"

Although jellies are almost never imported for the hobby (at least in the US), jellies are apparently becoming all the rage in the hobby in Japan (e.g., see http://www.austin360.com/news/03march/20/20jellyfish.htm).

Jellies are obviously popular, because aside from the hobby craze in Japan, institutions around the world (such as the Monterey Bay Aquarium) are now trying to add jelly displays to their permanent exhibits.

So, now that we have the basics out of the way, lets look at where you could get some jellies, and which ones are reasonable to keep?

WHERE DO YOU GET JELLIES?

Well, as I'm sure you know, the Petco/Petsmart on the corner is not going to have a tank of jellies.

Most large shipments of live rock will probably have a number of hydroids included, and if they make it through the curing process and are well fed, they will often mature and may start to release medusae.

Although this is not extremely common, many people have contacted me over the past several years asking about the jellies they have found in their aquaria, and from where they came.

More often than not, these animals are not suited to the design of a reef tank (although some species have suckered tentacles that can creep about the tank, and seem to thrive in well-established reefs), and they frequently die off.

If moved to a tank specially devoted to them, however, these species often thrive, and I have gotten a couple of my jelly tanks started in this way.

The exception to the generalization that jellies don't do well in your tank is for people maintaining seahorse tanks - in these low-flow, high-food environments, the jellies often thrive and can, in fact, become a "pest." (I have been talking to several people lately that are having problems controlling the jelly populations in their seahorse tanks).

So I guess that wasn't very informative, was it? There was no address to write, no number to call, no mail order company to contact. Well, that's because there are not a lot of places that offer jellies for sale. (although I'm sure I'll get a flood of Emails saying "We sell them" as soon as this is over).

WHICH SPECIES OF JELLIES ARE REASONABLE TO KEEP?

Ctenophores are a group about which relatively little is known, both in terms of biology and the hobby. Some ctenophores occur in coastal waters and are relatively hardy (e.g., Mnemiopsis, Pleurobrachia, and Beröe).

Some are even benthic and creep about the tank extending their tentacles into the water column from the glass.

Others are "blue-water" (only occur in the open ocean, far from shore) species which rarely survive contact with any solid objects (e.g., Cestum - the "Venus' Girdle" - often explodes on contact with the inside of a Ziplock bag during collection attempts). Obviously, such fragile forms are not well-suited to aquarium culture attempts.

Because their sting can be very dangerous, Cubomedusae should not be considered for a home aquarium, and we will not discuss the Cubozoans any further here.

The cnidae (specialized stinging cells) of many hydromedusae and schyphozoans, however, are incapable of penetrating human skin (although there are many exceptions), and therefore those species are reasonable choices for home aquaria, providing that you have an aquarium of appropriate design and size (we'll get back to this later).

For some species of hydro- and scyphozoans the dietary needs are known, and for others the animals appear hardy enough that they do not care what they are fed. With such species it is possible to culture the jellies and have a reasonable chance of success.

So what are some of those "reasonable choices" to start a jellyfish tank? Well, I have kept a number of species, but Aurelia aurita, the moon jelly, and Cassiopeia andromeda the upside-down jellyfish were the easiest species to maintain that produce large attractive medusae.

Aurelia, is just one of the large, graceful pelagic jellies that inspire people to consider setting up a medusa tank in the first place. Aurelia is primarily a temperate (cold-water) species, but seems to survive just fine at the low end of room temperature.

If your home is in a cooler climate, or is well air-conditioned during the summer in warmer climes, these animals should prove easy to raise (the alternative is to chill the water).

Cassiopeia is a tropical species which is by far the most common, if not the only, jellyfish offered for sale in the pet trade. These medusae can be easily maintained in an aquarium, because they gain much of their nutrition from photosynthetic zooxanthellae.

These scyphozoan jellyfish actually lack tentacles, and instead have highly modified "lips" on the manubrium (extendible mouth). The frills on the manubrium are interspersed with bladder-like growths (which can range from dull brown to bright purple in color, and millimeters to inches in length) which house concentrated zooxanthellae.

Having said that however, I have found that they need an inordinate amount of light, and have only flourished in a tank with a very high lighting output in my experience (higher than most SPS reef tanks!).

I have also found that like virtually all other "photosynthetic Cnidarians" they need to be fed regularly.

The frilly lips are loaded with nematocysts which are remarkably efficient at capturing small prey (enriched Artemia are a reasonable choice). Five adults were capable of clearing a 2 liter culture of newly-hatched Artemia from their tank in about 10 minutes - that's faster than my reef tank complete with corals and fishes! Pretty impressive for a species that "doesn't feed."

The nematocysts can also be released into the water column if the animal is disturbed (when swimming through large swarms of these animals divers often experience a sensation likened to swimming through soda water - the bubble-popping sensation derives from the freely-floating nematocysts firing when contacting the skin).

Although it is unlikely that anyone will experience an serious reaction to the sting of the upside-down jellyfish, some people have reported painful swelling in response to direct contact (and contact with sensitive areas of skin, such as the forearm are usually immediately noticable).

As an interesting side note, it was my experience that these animals would only reproduce sexually when there was detectable levels of ammonia in the system.

I thought that my experience may have been unusual, but after speaking with aquarists at the Monterey Bay Aquarium, I was told they found the same thing with their display (they didn't notice any reproduction until they doubled the halide lighting on the tank, started to feed regularly and took out all filtration).

I have only found these animals in the wild in eel-grass beds and mangrove swamps throughout Florida and the Caribbean, where there is relatively high decomposition and low water exchange relative to the reef environment.

This sort of environment tends to have measurable amounts of ammonia in the water, and I think that the zooxanthellae may need the nutrient supplement to meet the energetic requirements of the jellies.

WHAT SORT OF TANK SETUP DO I NEED?

It depends on the species which you intend to keep.

For Cassiopeia, you don't really need anything special. A large, well lit aquarium without a filter (but with an air-driven or gentle pump-driven water flow) seems to work just fine.

The medusae of Aurelia, on the other hand, are large and graceful attractions, but like all pelagic jellies, are built for the open sea, and are therefor poorly adapted to life in an aquarium.

There are many gelatinous species that are simply too fragile to ever be practical occupants in home aquaria, but many species are hardy enough that they can be easily maintained in an aquarium if it is specifically set up for them.

There are basically 3 designs that you can try depending on how much time and money you have to dedicate to your setup, how large the animals are, and how sensitive are the species you plan to culture. I will discuss all three of them in only brief detail here (we don't have time to get into great detail).

The first two are simple and cheap, but also pretty hard on the animals -- if you insist on trying to keep sensitive species, you should skip directly to the third option.

The first method is to use a simple hexagonal tank in which you set a large sponge filter (the larger the filter, the more diffuse the suction of flow through it) with an undergravel uplift tube covering the airline and the rising bubbles (if bubbles escape they can easily get into the swimming bell of the medusae and damage them or trap them on the surface).

The plastic uplift tube should end slightly above the water surface so that any water moved up the tube by the bubbles is dropped back into the tank, breaking the surface tension and aerating the tank. This will also help to push any jellies on the surface back down into the water column.

By running bubbles up the tube at the appropriate speed (a few per second) you should get very gentle turnover in the tank, but not run the risk of sucking all your jellies into the filter. I maintained a tank like this with a healthy tropical hydromedusa culture for about 3 years.

In the past, when I set up a jelly tank, I would simply use a very diffuse flow-through system to keep the medusae in suspension. One simple way to do this is to use a small canister filter to move water from one end of the aquarium to the other.

To do this you would set a spray bar across one edge of a large aquarium (say the left side) aimed toward the glass, and the intake at the other end of the tank (in this case, the right).

Then both sides of the tank would be sealed off from the central portion by hot-gluing a section of fiberglass mosquito mesh across the aquarium about 6-10 inches (depending on the strength of your filter) from each end of the tank (the more powerful filter you get, the more space you'll have to cut off each end of the aquarium.

Obviously, if you're going to "waste" 12-20 inches of your aquarium length, it had better be a long tank, so keep that in mind when the urge to put a large filter on your tank strikes you (I used a Fluval 103 pump on a 55 G tank - I have used tanks as small as 27 G, but wouldn't try to go much smaller than that).

The purpose of the mosquito mesh is to allow for undisturbed flow from the intake to the spray bar, but simultaneously prevent areas of high flow or suction that are likely to trap or damage the medusae.

The jellies can then be kept in the central portion of the tank because the flow through the mosquito netting is so diffuse that the medusae which contact it can easily swim away of their own accord.

There is also no reason that you couldn't keep other animals (that are stronger swimmers - such as seahorses, for example) on the ends of the tank, because any Artemia which escaped through the mesh would simply become food for either the jellies in the central portion or the animals on the ends of the tank.

In that way you could set up a very interesting display with smaller fishes on the ends of the aquarium and the medusae in the center, but keep in mind that you have a VERY small filter on the tank and need to keep the bioload down to maintain water quality!

This is basically the technique I and others have used to keep jellyfish alive for research purposes, but those tanks are almost always flow-through, so there was no need for the recirculating filter (natural sea water was simply pumped into one end of the tank, and drained back into the ocean at the other).

The final method is the most complicated and expensive, but also the most likely to succeed of all. You could build or buy a special tank designed to house your jellies in suspension at all times (called a kreisel).

These large circular tanks, which institutions like the Monterey Bay Aquarium use to keep their gelatinous zooplankton, are basically a large ring sealed between 2 flat panes of glass.

The ring has an opening along one side where water is piped through a thin tube slowly back into the tank, and a small overflow that allows excess water to dribble over the edge to a reservoir at the bottom.

A small pump, basically similar to a dosing pump, is used to deliver water from the reservoir back into the tank.

This constant flow of water, directed along the wall of the ring, causes a swirling current in the tank which forces the animals towards the center of the tank, and prevents them from either settling out of the water column or being trapped by the water movement.

This is a serious undertaking (you'll have to specially order or design and build your own tank if you intend to try this - although Dane Tullock was talking about posting a DIY design for a pseudokreisel sometime soon), and will probably not be a common sight in home displays.

There are many other methods that have been successfully used to maintain jellies, but I'm going to quit there :)

GETTING ON MY SOAPBOX

I'm not sure that the rarity of jellies in the pet trade is at all a bad thing. I still don't think that the average hobbyist is ready to set up and maintain a jelly tank at home. That sounds pretty harsh, doesn't it? Why would I say something like that?

Despite the craze of the jelly hobby in Japan, my understanding (although I've never been there to check) is that the goal of the hobbyist is simply to keep the adult medusae alive for a while and then replace them.

From the reports I've heard, it doesn't like there is any effort to complete the life cycle and maintain the jellies through multiple generations. The animals are seen as the "goldfish bowl" of marine pets.

They are relatively cheap and they just considered disposable - you keep them until they die, then replace the adults.

I'm sure many of you will ask, "What's wrong with that? That's how fish tanks around the world are maintained, and we're not complaining about that!"

I think this mentality is similar to most people who buy Orchids in the US. Sure there are some people who are willing to put in the effort to maintain an ugly plant for a year before it flowers and then enjoy the blooms, but most people always want the flowers.

There are actually a couple of locals who make a living off selling flowering orchids for around $20-50, and then buying back the finished plant for $5-10 credit towards the next blooming plant.

I suspect this is the same mind-set as many people interested in the jellyfish trade. The polyp stage is easy to keep and necessary for the release of the medusae, but it sure isn't as pretty. How many people are willing to set up and maintain an "ugly tank" to farm the release of the jellies?

If you are interested in setting up a disposable "jellyfish bowl" I hope you to realize that the collecting and shipping mortality of these animals is phenomenal, and until the trade advances to the point where suppliers recognize and prepare for the unique needs of these unusual animals, we shouldn't encourage their importation.

BUT, if you are willing to set up and maintain a tank of the polyp stage to farm the medusae, then I whole-heartedly encourage you to try.

Despite the rarity of these beautiful animals in the hobby at this time, I think that it is possible to keep many of these animals successfully (I and many others have done so for research purposes).

I hope that with a bit more time and information others may start to keep these animals for home displays as well.

At one point I had a bloom of umbrella jellyfish that at times looked like snow in the tank. I've wondered if these might have been planktonic feather dusters, but I have observed tiny clear guys pulsing through the water. Any idea on how to "seed" tiny jellies (besides getting lucky)?

Like I mentioned, these are not uncommon along with shipments of live Rock -- you get a bunch of the polyp stage and as you feed them and they start to grow, they eventually start to release medusae. That is cool, and it is easy to do if you have the polyps in your tank, but it is getting the polyps that is the difficult part. Maybe some of the folks that I have been talking with who have them will take my suggestion and start offering the polyps via MO for some of these easy to raise species :) I haven't seen the polyps offered by any MO or aquarium shop to date. The fact that you can't seed your tank from a friends tank with the jellies is not surprising -- it is the polyps (fuzz on the rocks) that you need to seed your tank, not the jellies in the water column. I have talked about this with one of my office-mates who is even more into jellies than I am, and she claims that there is no predictable way to get strobilation. She can induce it with a variety of forms of shock (light or temperature). It obviously varies by species a lot, and according to many by the time that you look at it. The results can be very convincing one experiment and completely the opposite in the next. I still think we lack a basic understanding of the biology of these animals.

What's a medusa?

A medusa in the generally free-living life stage of the cycle that is commonly referred to as a jellyfish. The difference is that many things that rlook like jellyfish are not -- they are colonies of specialized polyps that take the function of various parts of the body of a jellyfish. A jellyfish is a single individual, whereas a colony of polyps is all 1 genetic individual, but each part of the animal is composed of a different "individual" (much like the individual polyps of a coral form the head).

I have seen several life cycles of Nausithoe sp. jellies in my system. I usually only see the polyp stage. I have never actually seen the jelly fish stage. Are they too small to see, or perhaps only come out at night?

I'm pretty sure that they don't just come out at night -- there are medusae that spend most of their time at depth during the day, and there are plenty of tiny (1-2mm) medusae, but I suspect that you'd notice the animals if they were swimming around. It may be one of the hydrozoans that have a pulsating gonozoid (reproductive polyp) but never a detached medusa. I'll check for you.

What about the ultimate size of Aurelia in captivity...problems foreseen?

They can get pretty big, which is why I added that little "soapbox" bit at the end. I heard that Aurelia are one of the popular species in Japan, and that the animals were generally kept in small tanks (check out that URL for a picture to get an idea of the tank size). If we're not going to provide a reasonable habitat for the animals to survive, I don't think they should be kept (at least that's my opinion).

Couldn't you make a kreisel like tank out out a large diameter hexagonal tank, or even octagonal or more sides?

Not really -- you can try to set up a tank like this (as I mentioned) but it's pretty hard on the animals. You can set up a "whirlpool" design that will keep the animals in the middle, but there is nothing to keep them from settling out of the water column. When they hit the bottom in a tank like this, they actually seem to have a harder time getting up into the water column again. The easiest tank to set up is one that rotates on a "ferris-wheel" like motor -- these are called plankton wheels. The plankton wheel is a nice design for keeping everything in suspension, but it is a lousy design for trying to view your animals.

What is the best quick antidote to one of their stings?

You'll laugh, but urinate on the sting. Actually if you have meat tenderizer or household ammonium available, that would be a better choice, but in an emergency, urine works pretty well :)

How long have jellies survived in public aquariums?

That is a good question, and I'm afraid that I don't know the answer. I'm sure it depends on the species. I know I've had Cassiopeia for ~3 years in a tank. I'm going down to visit the folks in Monterey soon, and I'll ask them their record for survival.

I have never noticed the polyps in my tank or any jellies, what exactly am I looking for?

The polyps look like a fuzzy mat of the tiniest anemones you've ever seen. They often look more like a hairy mat on some surfaces of the rock than a cnidarian at all. Other times they look really obvious, and sometimes, no matter how hard you try, you're unlikely to find the polyps at all. If you feed your tank regularly and have never seen jellies, chances are fair that you don't have the polyps in your tank.

What is the common name of those E Coast jellyfish that look like they ate a couple of cheerios--are they combs?

I doubt it -- the comb jellies look like a marble that has 8 sparkly bands around it. I am not sure to which species you are referring, but there are many that could fit that description. The "cheerios" (great description :) are most likely the gonads -- that is the reproductive organs where the sperm and eggs are produced.

Rob, have you (or anyone) succesfully kept the smaller sea nettles or sea thimbles? (Linuche spp)

I believe Claudia Mills has kept Linuche. I have never tried it, but Claudia is amazingly successful when she sets her mind to keeping even "impossible" species, so I don't know whether or not that really counts as a "success" -- guess that's why she's one of the world's experts on jellies.

I have a rapidly spreading grey mold on one rock, which I now think may be a jellyfish polyp (nest). I have noticed tubes that form a sort of siphon. Can they go dormant?

I suspect that it is more likely to be a tunicate than a jelly polyp mat. The hydroid mats tends to look a lot like a low-lying hairball to the naked eye, and if you can see a siphon, it is likely to be a Urochordate (commonly called Ascidians or Tunicates). These animals are filter feeders that use a pharygeal basket to clear the water of algae and detritus as they grow. The siphon in one of two (usually in colonial forms one is virtually invisible) that they use to pump water through their bodies as they filter it. They are cool animals and are not often seen to flourish in reef tanks -- consider yourself lucky.

Thanks for the talk, Rob!

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