Sealed Palmtop reef for h. zosterae

Dear Brandon:

There are two primary issues you will need to address if you want to attempt to keep dwarf seahorses (Hippocampus zosterae) in your sealed PalmTop pico reef tank that I can foresee — the water flow and the issue of hydroids.

Dwarf seahorses are ambush predators that lie in wait until suitable prey passes within striking distance, whereupon they will slurp up micro crustaceans from the water column that pass within reach. They are deliberate feeders and when there is a appreciable water current that whisks potential prey past them too fast for them to target and slurp up, they are unable to eat. In order to avoid this sort of complication, you would need to greatly reduce or attenuate the water circulation in your pico tank, and this is going to be contrary to the needs of the SPS corals, which require strong water movement in order to thrive. I am thinking that it’s going to be very difficult to find a flow rate or achieve a water circulation pattern that would both be suitable for the live corals and allow the dwarf seahorses to feed upon rotifers, Artemia nauplii, and other micro crustaceans from the water column undisturbed.

Secondly, in order to keep the dwarf seahorses well fed, you will need to supplement the available pods and microfauna in the pico reef with regular feedings of rotifers or newly hatched brine shrimp, and, sooner or later, this WILL trigger an explosion of hydroids in any reef tank, regardless of how mature it may be or how uncommon hydroids are in such a system initially.

Sooner or later hydroids will appear in any marine aquarium that is receiving regular feedings of rotifers, copepods, or baby brine shrimp or plankton suitable for feeding dwarf seahorses. It’s inevitable because the hydroids can can gain entry into the aquarium in many ways. For example, they are notorious hitchhikers. Both the colonial polyp stage and the free-swimming micro-jellies can thumb a ride on live rock, macroalgae, hitching posts, sand or gravel, specimens of all kinds, or within so much as a single drop of natural seawater (Abbott, 2003). Beware of fuzzy looking seashells! Very often hydrozoans come in on the shells of the hermit crabs or snails we purchase as aquarium janitors (Abbott, 2003). Or they may be introduced with live foods, or even among Artemia cysts, in some cases it seems. They can even be transferred from tank to tank in the aerosol mist arising from an airstone or the bubble stream of a protein skimmer.

It can be very challenging to identify hydroids because there are about a zillion different species of hydrozoans and the different types have different characteristics and are often vary remarkably in appearance. There is considerable variation within the species as well, and the same type of hydroids can appear vastly different depending on the size of the colony and its stage of development, conditions in the aquarium, and their predominant diet. And, of course, the different stages of the life cycle of these amazing animals are so entirely different that they were long believed to be different types of cnidarians altogether, and different species names were often assigned to the same hydroid in different phases of its life cycle. Because they are so difficult to identify and are not easy to distinguished with the naked eye during their initial stages, hydroids often go undetected in nursery and rearing tanks until they begin to take a toll on the fry.

The typical hydroid colony has a stem with a variable number of polyps growing on it, and each of these polyps bears numerous tentacles that are liberally studded with knobby nematocysts (batteries of deadly stinging cells). There are many different kinds of hydroids and they appear in the aquarium in many different guises: many colonies are stalked; some have fingerlike projections, others look like tiny pink fuzzy balls or appear like cobwebs (the webbing kind usually spread along the bottom or grow on the aquarium glass along the substrate). The "snowflake" type of hydroids seem to be particularly common in aquaria, whereas other species look more like crystal chandeliers, and some species form bushy colonies as they grow that serve as microhabitats for Caprellid skeleton shrimp and other tiny crustaceans.

Even a large hydroid colony appears harmless to the naked eye of the untrained observer. It takes a much closer look to reveal the dreaded ‘droid’s lethal nature, as described below:

"Studying the colony under high magnification, one soon becomes lost in an extraordinarily complex, living world–a microcosm in which a beautiful but deadly ballet is conducted on a microscopic scale (Rudloe, 1971). Hungry polyps, some resembling snapdragons, others looking more like daisies or tulips, expand their knobby, translucent tentacles, slowly flexing and languidly waving them about, lulling the observer with their slow-motion ballet — until they abruptly and quite unexpectedly snap up a bit of planktonic life, stinging it, drawing it in with one violent contraction, digesting it, and then re-expanding like a blossoming flower to hunt again (Rudloe, 1971). There are many such polyps in a colony, hundreds of them, each of which is armed with many tentacles and countless nematocysts, and at any given moment, some of them will be dormant and still, some will be expanded and lazily casting about for prey (Rudloe, 1971), and still others actively feeding (Abbott, 2003)."

The feeding or nutritive zooids are the distinct individual animals in a hydroid colony that are responsible for capturing and digesting prey; as such, they bear the nematocyst-studded tentacles. But you need high magnification in order to appreciate the true beauty of living hydrozoans, or to differentiate between different species of hydroids, or to observe the zooids going about their deadly business.

Hydroids are insidious because they start out so small and insignificant, yet spread so quickly under ideal conditions (e.g., a nursery tank or dwarf seahorse tank receiving daily feedings of Artemia nauplii). Many species can spread asexually by fragmentation as a microscopic speck of the parent colony. All of the troublesome types have a mobile hydromedusae stage, which look like miniscule micro-jellyfish, and can spread sexually in this way as well (Rudloe, 1971). The mobile medusae swim about with a herky-jerky, pulsating motion and are often mistaken for tiny bubbles due to their silvery, transparent, hemispherical bodies (Rudloe, 1977). These tiny jellies often go unrecognized until they begin to settle and are discovered adhering to the tank walls. They will have a large "dot" in the middle of their bodies and smaller ones at the base of their nematocysts (Abbott, 2003). Both the polyp stage and the medusa stage sting (Rudloe, 1977) and are capable of killing or injuring seahorse fry. Multiple stings can kill the babies outright, but they are often only injured by the nematocysts, which damage their integument and leave them vulnerable to secondary infections. Many times it is a secondary bacterial or fungal infection that sets in at the site of the injury which kills the fry.

Once they find their way into a dwarf seahorse setup or nursery tank, hydroids can explode to plague proportions very quickly because conditions are ideal for their growth: perfect temperatures, an abundance of planktonic prey that is renewed every few hours, and a complete absence of predators.

When hydroids become a problem in the nursery or dwarf tank, Brandon, which is inevitable in a reef system, the only really effective treatment for eradicating hydroids is to treat the tank with fenbendazole (brand name Panacur), but unfortunately, this medication would also devastate many of the corals in the aquarium, as discussed below:

Eliminating Hydroids

Hydroids can be controlled in the aquarium by using a medication known as fenbendazole to treat the tank over a period of days. Fenbendazole (brand name Panacur) is an inexpensive anthelmintic agent (dewormer) used for large animals such as horses, and the de-worming granules can be obtained without a prescription from stores that carry agricultural products (e.g., farm and ranch equipment, farming supplies and products, veterinary supplies, livestock and horse supplies, livestock and horse feed). If you live in a rural area, those would be good places to obtain it as well.

However, there are a couple of things you should keep in mind when treating an aquarium with fenbendazole, Brandon. Administering a regimen of fenbendazole (FBZ) or Panacur will eradicate any hydroids, Aiptasia rock anemones, or bristleworms from live rock or live sand, thereby rendering them completely seahorse safe. The recommended dose is 1/8 teaspoon of the horse dewormer granules (22.2% fenbendazole) per 10 gallons of water. Dose aquarium with 1/8 teaspoon/10 gallons every other day until you have administered a total of 3 such treatments (Liisa Coit, pers. com.). Even one dose will do a fine job of eradicating bristeworms, but Aiptasia rock anemones and hydroids are a bit tougher and may require 2-3 doses to eliminate entirely.

Because fenbendazole is essentially a de-worming agent, it will destroy any bristleworms, flat worms, spaghetti worms or the like. The FBZ or Panacur treatments are best administered to the live rock in a bucket or hospital tank before the LR is introduced in the main tank. Otherwise, the massive die-off of the worm population in the aquarium may require large water changes in order to prevent a dangerous ammonia spike! And after the treatment is completed, its a good idea to add a portion of newly purchased live sand to the system in order to help restore its normal diversity of fauna and microfauna again (Liisa Coit, pers. com.).

Fenbendazole does not have any adverse effects on biological filtration, but be aware that it is death to many Cnidarians besides hydroids. Mushrooms and related corals are generally not affected, but expect it to have dire effects on other corals (e.g., sinularias), polyps, gorgonians, and anemones. In general, any Cnidarians with polyps that resemble the stalked family of Hydrozoans are likely to be hit hard by fenbendazole, so don’t use this treatment in a reef tank!

Also be aware that fenbendazole seems to soak into the porous live rock and be absorbed indefinitely. I know one hobbyist who transferred a small piece of live rock that had been treated with fenbendazole (Panacur) months earlier into a reef tank, where it killed the resident starfish and Astrea snails. So enough of the medication may be retained within treated live rock to impact sensitive animals months after the fenbendazole was administered. Don’t treat live rock intended for reef systems with fenbendazole (Panacur)!

At the lower dosage recommended for nursery tanks and dwarf seahorse tanks with fry (1/16 tsp. per 10 gallons), fenbendazole normally does not harm cleaner shrimp and decorative shrimp. With the exception of Astrids (Astrea), Coit and Worden have found it does not usually affect the types of snails typically used as cleanup crews (e.g., Nassarius, Ceriths, and Nerites). It will kill starfish but copepods, hermit crabs, and shrimp are normally not affected.

Macroalgae such as the feathery or long-bladed varieties of Caulerpa or Hawaiian Ogo (Gracilaria) are not harmed by exposure to fenbendazole at even triple the normal dose. In fact, if you will be using Caulerpa in your nursery tanks to provide hitching posts for the fry and serve as a form of natural filtration, it’s a very wise precaution indeed to treat them with a regimen of fenbendazole beforehand.

So fenbendazole (FBZ) or Panacur is primarily useful for ridding bare-bottomed nursery tanks and dwarf seahorses setups of hyrdroids and Aiptasia anemones, ridding Caulerpa and other macroalge of hydroids or Aiptasia before its goes into the aquarium, and cleansing live rock of bristleworms, hydroids, and Aiptasia rock anemones before it is introduced to the aquarium.

It can also be used to eradicate bristleworms, hydroids, an Aiptasia from an established aquarium if it does not house sensitive animals such as live corals and gorgonians, starfish, Astrea snails, or tubeworms and other desirable worms that may be harmed by FBZ, providing you monitor the ammonia levels closely and are prepared to deal with the ammonia spike that may result from the sudden death of the worm population.

In summation, sir, if the aquarium with a hydroid problem will be housing live corals at some point, it would be best not to treat it with fenbendazole. And you may not need to be concerned about the hydroids in the first place, since as long as you keep them out of your nursery tanks, hydroids won’t present a problem for large seahorses like Mustangs and Sunbursts (Hippocampus erectus) at all. They are impervious to their stings. In fact, in the wild, seahorses often encourage algae, small bryozoans and other encrusting organisms, including hydroids, to grow on their exoskeleton in order to enhance their camouflage (Vincent 1990). The hydroids are only a problem for baby seahorses in nursery tanks or for the tiny dwarf seahorses, which are susceptible to their stings.

In short, Brandon, even if you can overcome the problem with water flow, I suspect that you are going to have an ongoing battle with hydroids in a pico reef tank that houses dwarf seahorses, and you may then find yourself in the difficult position of either sacrificing the pigmy ponies for the sake of the live corals or treating the tank with fenbendazole and sacrificing many of the corals for the sake of the seahorses.

This is an interesting project, sir, and worth experimenting with, but I cannot see how you will be able to overcome the hydroid issue in the long run in such a setup…

Best wishes with all your fishes (and invertebrates), Brandon! Please keep us posted if you try keeping dwarf seahorses in these interesting ecosystems — I know we would all be interested in the results of this most interesting experiment.

Respectfully,
Pete Giwojna

Dear Brandon:

Thank you for all of your kind words, sir! Anyone with an interest in the care and keeping of seahorses is always welcome to post on this forum; it does not matter how many other discussion boards or forums you may participate in, or where else you may choose to post, now or in the future — you are always welcome here.

Regarding raising dwarf seahorses (Hippocampus zosterae) using frozen Cyclop-Eeze, I have serious reservations about its usefulness as a food for this species, Brandon. The problem is that dwarf seahorses are pretty lazy hunters (actually the technical term is "ambush predators"). They like to anchor their tails to a convenient hitching post and wait for their food to come to them, rather than chasing after potential prey. If a food item drifts by them outside of easy reach, they normally won’t swim after it or make any attempt whatsoever to pursue it; rather, they will typically simply ignore it and wait for another morsel to come their way that’s within striking distance. That’s okay with live foods such as newly hatched brine shrimp (Artemia nauplii), since they will survive indefinitely in saltwater and swim around until they blunder within striking distance of one of the dwarfs and get eaten. But it’s a big problem with nonliving food which drifts slowly down to the bottom once it’s added to the aquarium — unless it just happens to drift right by the snout of one of the hungry dwarf seahorses, it won’t get eaten and will just accumulate on the bottom of the tank. As you can imagine from what I’ve already told you, dwarf seahorses have no interest whatsoever in food after it has settled to the bottom, so it gets ignored until it begins to decay and degrade the water quality (which can go downhill awfully fast in the small dwarf seahorse setups, such as a pico tank.) Although if it is prepared and offered properly, the Cyclop-Eeze may stay suspended in the water column pretty well in reef tanks, which feature very vigorous water movement for the sake of the live corals, the circulation in dwarf seahorse tanks must be very gentle, which usually means that the frozen Cyclops settles to the bottom all too quickly.

I can tell you that many attempts have been made in the past to get dwarf seahorses to eat frozen baby brine shrimp or frozen Cyclop-eze, and these experiments almost always fail for the reasons mentioned above. In most cases, attempting to get them to eat frozen food or nonliving prey just results in polluting your aquarium. I don’t believe the Cyclop-Eeze would fare much better than the frozen baby brine shrimp or the Instant Baby Brine Shrimp others have tried in that regard, Brandon. You just cannot count on adult Pixies or dwarf seahorses to eat frozen baby brine shrimp or any other frozen foods consistently.

It can sometimes be done with lots of time, patience, and perseverance, and it isn’t really as difficult as most folks imagine to train adult dwarves to eat frozen foods IF you have a role model to teach them. Zulus, tubers, barbs, young erectus, etc. all make great teachers, and most adult zosterae will learn to take bits of frozen mysis or sometimes the frozen form of Cyclop-eeze readily enough with such role models to show them the way. But some dwarves just don’t get it and never learn to eat frozen fodder and, in my opinion, it’s just not worth the effort of trying to train any of them.

Why? Because training adults to eat frozen food by no means frees the dwarf seahorse keeper from the need to hatch out huge amounts of baby brine shrimp every single day. Think about it. Anybody who keeps any amount of dwarf seahorses always has zosterae fry on his hands. The fry need copious amounts of newly hatched Artemia nauplii daily anyway, so it’s simply easier and more efficient to hatch out enough bbs for the adults at the same time. Many hobbyists prefer to raise dwarf fry in the same tank as their parents, so maintaining an adequate feeding density of Artemia nauplii for the newborns automatically assures that the adults are equally well fed. For me, there’s just no percentage in spending a lot of time and effort trying to train adults to eat frozen food when I still have to keep a battery of brine shrimp hatcheries cranked up full blast for the babies anyway. (It is normally not feasible to train newborn dwarf seahorses to feed on nonliving foods until they are several weeks old.)

In short, Brandon, it would be an interesting experiment to try to teach dwarf seahorses to eat the Cyclop-Eeze, which they may recognize as potential prey. It could possibly work out if you could achieve just the right balance of gently up-swelling water flow to keep the Cyclop-Eeze spend and slowly circulating through the tank, rather than settling to the bottom right away, but that’s a tricky proposition that would likely require a lot of trial and error to figure out before you got it just right…

It’s worth a try, but you shouldn’t count on such of feeding regimen to be successful. If you’re going to set up a tank of Pixies or dwarf seahorses, you must be willing to provide them with daily feedings of newly hatched brine shrimp should the experiment fail at some point, which I suspect would be the case.

Anyway, those are my thoughts on the matter for what ever it’s worth, Brandon.

Dwarf seahorses survive in the wild despite the presence of hydroids, anemones, and other stinging animals because the density of these cnidarians is so low in the vastness of the ocean. In a small aquarium — particularly a nursery tank or a dwarf seahorse setup that is receiving daily feedings of rotifers, copepods, or newly hatched brine shrimp (Artemia nauplii) — hydroids grow and multiply rapidly, to the point where it is very difficult for the dwarf seahorses or their fry to avoid coming in contact with them (especially the mobile hydromedusae stage). In the vastness of the sea, this does not happen — the hydroids are dispersed far and wide by the ocean currents and tides and the hydroids have many natural predators in the wild, such as nudibranchs and certain gastropods, which feed on the adult colonies (the nudibranchs will even absorb the stinging nematocysts from the hydroids and incorporate them into their own bodies as a means of defense), as well as many fishes and invertebrates that prey on the mobile hydromedusae (the reproductive stage of the hydroids). As a result, the hydroid colonies in the limitless coastal seas are relatively few and far between, and dwarf seahorses do not often come in contact with.

In other words, Brandon, hydroids, anemones, and other cnidarians don’t pose a serious threat to dwarf seahorses in the wild because of the patchy distribution of the stinging animals and the mobility of the pigmy ponies, which are always free to move away from an area where hydroids are present. It is much the same reason that marine fish in the wild are not wiped out by outbreaks of Cryptocaryon or Amyloodinium or any of the other parasitic infections that are the scourge of so many marine aquariums. In the vastness of the ocean, the fish that are parasitized by these pests are not continually reinfected as the protozoan parasites go through their life cycle. In the confines of the aquarium, however, the infectious stage of the parasite readily reinfests the same fishes that are contained within a small volume of water with them again and again until the fish are simply overwhelmed by the sheer numbers of the parasites that come to infest their gills. In the vastness of the ocean, these parasites do not pose a serious risk to marine fish, whereas in the limited water volume of a marine aquarium, they multiply rapidly and are soon out of control, killing off the fish via asphyxiation or secondary infections.

If you are willing to use lifelike artificial corals rather than living corals, Brandon, then there is an easy solution to the hydroid problem. In a case like that, you could simply maintain a very low dose of the fenbendazole (brand name Panacur) in your dwarf seahorse setup, which will effectively eliminate hydroids, Aiptasia rock anemones, and bristleworms from the aquarium without harming the dwarf seahorses and their babies in the least. You would have to do without the sort of live corals that are sensitive to the fenbendazole, as well as avoiding feather duster worms and certain snails that would be harmed by the Panacur, but you would have no concerns about hydroids or other stinging animals taking a toll on the dwarf seahorses.

I find the best approach for dwarf seahorses is to include the live rock, treat the tank with a regimen of fenbendazole (brand name Panacur), and allow the porous live rock to gradually leach out small amounts of the fenbendazole thereafter to provide the dwarf tank with foolproof hydroid protection for the next several months. The fenbendazole also destroys Aiptasia rock anemones and bristleworms, which are the other problematic pests which might present a problem in a dwarf seahorse tank that includes live rock. So keeping live rock in your dwarf tank and treating it with fenbendazole renders the live rock pest-free and perfectly safe for use with dwarf seahorses, allowing you to take advantage of the many benefits live rock provides for the aquarium, including the control of nitrates and offering stability to the inherently unstable small dwarf seahorse tanks.

In my experience, including live rock in your dwarf seahorse tank and treating it with fenbendazole is absolutely far and away the best method to prevent an outbreak of hydroids or Aiptasia rock anemones or hydromedusae jellyfish or other cnidarians, and is therefore the best way to protect your dwarf seahorses from these omnipresent pests.

Best of luck with your interested in dwarf seahorse project, Brandon.

Respectfully,
Pete Giwojna

Post edited by: Pete Giwojna, at: 2009/11/27 23:03