Re:Starting a 29 Biocube Seahorse tank

Pete Giwojna

Dear Jason:

Okay, sir, that was a fine idea to seed your 29-gallon biocube with saltwater and some of the live rock from your 120-gallon reef tank in order to accelerate the cycling process.

And the water temperature should be just fine, Jason. The comfort zone for Mustangs and Sunbursts is 72°F-77°F and it’s very important to avoid temperature spikes that approach 80°F or above for any length of time. If your water temperature is holding at 74°F-75°F, that will be just about ideal for the Mustangs and Sunbursts. (That’s a relief because many times the biocubes tend to run on the warm side and require chilling to make them suitable for seahorses.)

Regarding the water flow, Jason, in general you want the circulation pumps for a seahorse tank to turn over the entire volume of the aquarium at least five times per hour. In other words, for your particular tank, you need to maintain a turnover rate of at least 150 gph. If you are using a spray bar return that roils the surface of the aquarium to promote better surface agitation and facilitate efficient gas exchange at the air/water interface, which will diffuse and soften the output, you can maintain a turnover rate that is considerably higher (> 10 times per hour) without overpowering your seahorses. So the proper amount of water circulation will vary depending on the type of flow bar and pump(s) you are using.

This is what I usually advise home hobbyists regarding the water circulation for their ponies, Jason:

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Water Circulation for the Seahorse tank

Many seahorse keepers are overly conscious of the inactive life style and limited swimming ability of Hippocampus, and have adjusted their flow rates accordingly, resulting in undercirculated tanks with too little water movement. That’s a serious mistake for a small, close-system aquarium.

In actuality, seahorses prefer moderate water movement, including some areas of brisk current, providing there are also sheltered spots and some areas of relatively slack water they can move to when desired. Slack water means comparatively low flow, NOT stagnant conditions! As with any aquarium, avoid dead spots and stagnant areas in the seahorse tank at all costs (Giwojna, unpublished text).

Contrary to popular opinion, seahorses are quite effective swimmers that can hold their own in strong currents as long as sheltered areas are available (Delbeek, Oct. 2001). I have often discussed this matter with professional divers and collectors who regularly encounter seahorses in the ocean, and they report that the horses are often found where you would least expect them — well offshore and thriving in areas with powerful currents. For example, here is how Paul Baldassano, a commercial diver in New York who makes his living collecting sea urchins, describes the behavior of his local seahorses:

"In regard to seahorses in the wild, I occasionally see Hippocampus erectus in the wild while SCUBA diving but never in the places where they are supposed to be. I see them in the open sea far from shore and also in areas with large rocks and very strong currents. The last one I saw was in a channel off the south shore of Long Island New York in water about 12 feet deep. The current was so strong that I had to hold on to the rocks so as not to be swept away. This Hippocampus erectus was having no trouble staying there munching on the abundant plankton. Apparently they find places near the rocks where there is no current because as you know they are lousy swimmers. There is also a large population of seahorses in a similar area in another part of the New York shore, but I think it is best not to divulge that location for obvious reasons (Baldassano, pers. com.)."

Neil Garrick-Maidment, a very successful seahorse breeder in the UK, reports much the same thing, noting that seahorses in the wild seem to thrive amid strong currents:

"Whenever I have dived on Seahorse sites I have always been amazed by the currents and tides that this very fragile looking Seahorse lives in. We often find Seahorses in flat muddy/silt areas nowhere near rocks or weed. These areas are often scoured by strong currents and the Seahorses do well in them and seem completely unperturbed by the current (Garrick-Maidment, pers. com.). In setting up a tank for them I try to remember the feeling I had in those areas and replicate them. I have now started to use wave surge devices, so that the current in the tank, although strong (they seem to thrive in strong currents) varies in its direction (Garrick-Maidment, Jun. 2002)."

Kirk Strawn, who earned his Master of Science thesis studying Hippocampus zosterae in the field, echoes Neil’s thoughts on the matter:

"The aquarist is not giving his seahorses natural conditions when he keeps them in a still-water aquarium. In nature tidal currents, wind, and waves are usually mixing the well aerated surface film water with the deeper water."

Likewise, David Warland, a fish farmer and commercial seahorse breeder in Port Lincoln, Australia, reports he often finds Hippocampus abdominalis perching on the tuna net enclosures at the farm in deep water:

"The Horses that are around the farms have traveled vast distances over plain sand/mud to get to the farms, which are in at least 20 meters of water, and are miles from the nearest land or shallow water (Warland, pers. com.)."

And Jorge Gomezjurado, the Senior Aquarist at the National Aquarium in Baltimore, recommends the following when it comes to water movement:

"I personally believe that current and water dynamics are very important for Syngnathids. In nature they live in areas with active water movement.(i.e., tides in mangrove lagoons and estuaries, coral reefs, kelp forests, etc.). Why don’t we give them the same environmental conditions in captivity? Our small tanks (90 gallons) have large turnovers on an average of 5 gpm (or 300 gph). It is very important that the current is steady and directionally constant, which allows the animals to find a good spot to hold and they will not be pulling in different directions all the time."

Most seahorse keepers feel it’s best to keep the current steady and nonvarying so they can find slack-water areas and sheltered spots downcurrent to hold in when they want to get out of the current. The more brisk the water flow, the more important this becomes. However, in a large aquarium with low to moderate water movement, alternating currents should not present much of a problem, and would help to provide good circulation throughout the tank.

You’ll want to adjust the outflow the filters to eliminate any dead spots or stagnant areas where waste products may tend to accumulate. Good circulation will prevent pockets of harmful anaerobic decay and keep particulate matter suspended in the water column where the filters can remove it from the aquarium. Alternating the direction of the water flow is also helpful, as is increasing surface agitation to improve the oxygenation and facilitate more efficient gas exchange at the air/water interface. A simple air stone anchored just beneath the surface of the water can help to achieve this goal.

Using Powerheads for Additional Water Movement

If the external filter(s) do not provide enough water movement to assure good circulation throughout the aquarium, you can position small powerheads in the tank, strategically placed to provide good water flow wherever there might otherwise be dead spots or stagnant areas. Just make sure that the intake for the powerheads is screened off in order to prevent a curious seahorse from getting its tail sucked up by the powerhead and injured.

For example, along with an external power filter, my seahorse setup also has a 200 gph powerhead with a sponge pre-filter positioned right near the top for surface agitation and extra water movement, with additional small powerheads used as needed to eliminate any dead spots along the substrate or behind the rockwork. I like to give my seahorses as much current as they can handle without getting blown around.

You don’t need to use a large, powerful powerhead to improve the water circulation in your seahorse tank. A small unit will generally suffice as long as it’s positioned properly where it’s most needed, and using a device that automatically sweeps the powerhead back and forth will often allow you to produce much better water movement than a much bigger powerhead that is stationary.

Devices that will automatically alternate the water flow in the aquarium by rotating the water flow from side to side include the Power Sweep power heads by ZooMed, the OSCI-Wave by Bell Marine and the Sea-Swirl by Aquarium Currents.

The Power Sweep power heads have an automatic rotating outlet that can be used as a wave maker. They are inexpensive and come in a number of different sizes to suit most every aquarium but need to be well-maintained to keep them in good working order. In short, the Power Sweep powerhead is an automatic self-rotating wavemaker that comes in three different models, each with a different flow rate, measured in gallons per hour (GPH).

Power Sweep 214 – For aquariums up to 30 gallons (114 liters) with a flow rate of 160 GPH

Power Sweep 226 – For aquariums up to 50 gallons (190 liters) with a flow rate of 190 GPH

Power Sweep 228 – For aquariums up to 75 gallons () with a flow rate of 270 GPH

They all have an adjustable flow rate that will allow you get the desired flow for your particular setup, which is ideal for seahorse tank. They will fit all undergravel filter stem sizes and are an excellent addition to a seahorse setup that is filtered with undergravels, and they also come with a pre-filter for the intake and a mounting bracket with suction cups.

The OSCI-Wave uses an electric motor to control a single powerhead. Powered by a small AC motor, this unit is tank rim mounted and hangs a powerhead 4.5" below the rim of the tank, which it then rotates back and forth. The Bell Marine OSCI-Wave oscillator is a small motor, located inside a 5.5" long, 3" wide 2.5" tall black acrylic box, which is attached to the rim of the tank and suspends a powerhead up to 4.5" below the surface of the water. The box mounts on the frame of the aquarium with an acrylic bracket with 4 nylon screws. The powerhead of your choice is mounted on a paddle which is attached to a plastic shaft, suspended from the box. The motor, almost silently, sweeps the powerhead in a 90 degree arc every 30 seconds. The manufacturer (Bell Marine) recommends the use of Aquarium Systems Maxi-Jet powerheads, due to their small size for the high velocity output, but it can be used with most powerheads.

The Sea-Swirl is a rotating return device. It uses an electric motor to power the rotating return that oscillates the return water from your existing pump or canister filter 90 degrees every 60 seconds. These units are available in three different sizes, are mounted on the rim of the tank, and cannot be submerged. As a result, the Sea-Swirl agitates only the surface water and can’t be adjusted to point toward the bottom of the tank, which is a limiting factor for these units. They must be used with a separate powerhead, water pump, or canister filter.

All of these devices do a good job of increasing surface agitation and maximizing the water movement provided by a single powerhead to further improve water circulation. Which of them will produce the best results for you, if you need to increase the water circulation in your seahorse setup, depends on how you’ve chosen to set up your aquarium, its size, the equipment you already have, and on your available budget. For example, the units that are mounted on the rim of the aquarium can be difficult to mount on a tank with a full aquarium hood. If your local fish store does not carry them, just do a Google search for any of these devices and you will find numerous outlets that offer them online.

Improving the water circulation and surface agitation to increase the oxygenation will raise the levels of dissolved oxygen in the aquarium while eliminating excess CO2 via more efficient offgassing. You may notice that your seahorses become more active and have a better appetite, eating more aggressively, as a result, and elevating the levels of dissolved oxygen and reducing the levels of dissolved CO2 will also help to raise and stabilize the pH of the aquarium at the same time. This is important because the pH of the aquarium tends to drop over time, and low pH can be a contributing factor for gas bubble syndrome.

Providing good water circulation and surface agitation to improve the oxygenation and promote more efficient offgassing at the air/water interface is especially important for seahorses because of their primitive gills. Unlike most teleost (bony) fishes, which have their gills arranged in sheaves like the pages of a book, seahorses have rudimentary gill arches with small powder-puff type gill filaments. Seahorses are said to have "tufted" gills because they appear to be hemispherical clumps of tissue on stems. Their unique, lobed gill filaments (lophobranchs) are arranged in grape-like clusters and have fewer lamellae than other teleost fishes. Because of the difference in the structure and efficiency of their gills, seahorse are unusually vulnerable to hypoxia when CO2 levels are high and/or O2 levels are low, so the diligent seahorse keeper will take full advantage of the measures we have discussed above to improve the dissolved oxygen levels in the aquarium.

The point is that, as long as slack-water retreats are available, the greater seahorses can tolerate far more current than most folks suspect and good circulation is as important for a seahorse setup as any other aquarium. What seahorses lack as swimmers is not agility, but rather stamina (Evans, 1998). They can hold their own against strong currents, but not indefinitely, so low flow areas where they can move out of the current and hold when they want to rest must be provided in addition to good circulation.

In short, if your filtration is not turning over the entire volume of the aquarium a MINIMUM of 5 times per hour, your seahorse setup is undercirculated. With a spray bar return raised above the surface of the water to diffuse the outflow, you can safely achieved much higher turnover rates (> 10 times per hour) without producing too much turbulence or current for seahorses in a tall tank. A waterfall return is another good way to diffuse the output from your filter, and also works well for seahorses. There will be an area of relatively vigorous water movement at one end of the aquarium underneath and nearby the waterfall, while the other end of the tank is a relatively low flow area. (By the same token, however, if the filtration system in your seahorse tank is turning over the entire volume of water much more than five times per hour, it may be too overpowering for the seahorses unless it is diffused by a spray bar or waterfall return.)

As with anything, too much of even a good thing can be undesirable, and too much current can overwhelm the limited swimming ability of Hippocampus. One indication that you may have too much water movement in your seahorse tank is if the seahorses are getting buffeted around by the currents, and whisked away uncontrollably when they tire of fighting the current. Or alternatively, they may stay perched in one place all the time and refuse to swim around and explore their tank for fear of getting swept away by the current if they relax their grip on their hitching posts. So you can get a pretty good gauge of how well the seahorses are able to cope with the water movement than their tank by observing how the current affects the swimming ability.

Likewise, if a mated pair of seahorses is consistently spilling eggs during the copulatory rise, that’s another pretty good indication that there may be too much turbulence or water movement in the upper reaches of their aquarium.

If the seahorses are having difficulty tracking their prey and eating because the current whisks the frozen Mysis past them too quickly to target it accurately and slurp it up, that’s another red flag. Often that situation can be corrected simply by adjusting the output from your filter to reduce the current during feeding time or turning it off altogether while the seahorses are eating.

But as long as your seahorses aren’t getting buffeted around, aren’t routinely dropping eggs during disrupted mating attempts, and aren’t having difficulty targeting their prey and eating, there’s really no such thing as too much water movement. In general, the stronger the water flow, the more important it is to keep the water currents steady and unvarying so the seahorses can establish holding areas in the sheltered spots and low-flow zones without getting blindsided by unpredictable currents. Just make sure your seahorses are not getting trapped against overflows and be sure to screen off the intakes for any powerheads. Powerheads can be switched off at feeding time, if necessary.

The Importance of Surface Agitation

Because the height of the aquarium is an important consideration for a seahorse tank in order to allow the seahorses to mate comfortably during the copulatory rise and to protect them against depth-related conditions such as gas bubble syndrome, many seahorse keepers opt for tall hexagonal or column tanks rather than the usual rectangular aquarium setups. That’s just fine and hex tanks and column tanks can work very well for seahorses providing they are large enough and the aquarist is careful to provide them with good surface agitation in order to assure good oxygenation.

That’s important, because the amount of dissolved oxygen in an aquarium is dependent primarily on three factors: the surface area of the tank, the water circulation in the aquarium, and the amount of surface agitation in the tank. Gas exchange takes place only at the air/water interface or surface of the aquarium, which is where clean oxygen enters the aquarium water and dissolved carbon dioxide is off-gassed, leaving the aquarium. The greater the surface area of the aquarium, the more efficient this gas exchange will be, and the higher the dissolved oxygen levels and the lower the dissolved CO2 levels will be as a result. Likewise, good circulation throughout the aquarium will prevent dead pockets or stagnant areas, assuring that all the water in the aquarium passes over the surface for gas exchange on a regular basis. Surface agitation is important because no gas exchange can take place unless the surface tension of the water is broken. Therefore, the better the surface agitation, the more efficient gas exchange becomes and the better the aquarium will be oxygenated.

This is where hexagonal tanks and column takes are at a disadvantage. The surface area of such tanks is restricted, much reduced from the surface area of a standard rectangular tank of equal water volume. Hex tanks and column tanks thus have less surface area for gas exchange to take place, and it is very important for such tanks to have good aeration and surface agitation to compensate for this drawback. This is especially vital for the seahorse keeper, because our seagoing stallions are very vulnerable to low levels of dissolved oxygen (and high levels of dissolved carbon dioxide) because of their primitive gills structure. So if you will be using a hexagonal aquarium or column design for your seahorse tank, it’s especially important to you to provide good water circulation and surface agitation.

Employing wave makers, devices that automatically alternate the direction of the water flow, and using small powerheads to supplement water movement are all the more important when you are using a tall column tank or hexagonal aquarium. Ordinary airstones and bubble wands can also be helpful for providing surface agitation and improving water circulation, and they will do your seahorses no harm whatsoever as long as they produce relatively coarse bubbles and are positioned where the bubbles cannot be drawn into the intake for the water pumps or filters. Just keep the airstones, air bars, or bubble wands relatively shallow in tall tanks – no more than 20-30 inches deep, and they will help to maintain high dissolved oxygen levels while helping to prevent gas supersaturation.

Finally, it’s important for the seahorse keeper who uses a hex tank or column tank to monitor the levels of dissolved oxygen on a regular basis to make sure they remain nice and high. We will discuss the use of test kits to monitor dissolved oxygen in more detail in Lesson 4.
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Okay, Jason, that’s the rundown on water flowing water circulation in a seahorse setup. You’ll need to determine what turnover rate the Maxijet 404 is actually producing in order to determine whether you will need a Koralia nano powerhead for supplemental circulation.

Regarding the refugium, sir, Charles Delbeek describes a simple refuge that works very well with seahorse tanks as follows:

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A refugium is simply a self-contained protected area, isolated from the main tank but sharing the same water supply, which provides many of the same benefits as a sump. A refugium can help newly added fish or invertebrates easily acclimate to a new tank. It can provide a safe haven for injured fish or corals to regenerate damaged tissue without the need for a separate quarantine tank. But perhaps its main benefit for the seahorse keeper is provide a protected area where macroalgae can be grown and small live prey items (copepods, amphipods, Caprellids, etc.) that will eventually become a food source for the inhabitants of the main portion of the tank can be cultured safely, allowing their population to build up undisturbed.

For instance, Charles Delbeek likes to use colonial shrimp species in the refugium for his seahorse tank, where the regular reproduction of these hermaphroditic crustaceans will provide a continuous supply of nutritious nauplii for his ponies: "There is a method that can be used to offer an occasional supply of live food for your sea horses. By setting up a separate system housing several species of shrimp such as the common cleaner shrimp (Lysmata amboinensis), peppermint shrimp (Lysmata amboinensis), or Rhynchocinetes uritai or R. durbanensis, you can get a fairly regular supply of live shrimp larvae. These species are best to use since they can live in large groups and spawn on a regular basis. Such a system is commonly called a refugium. A refugium is a small (10-20 gallon) aquarium that contains live sand, live rock and/or macroalgae such as Caulerpa or Gracilaria. It is plumbed such that water from your main system is pumped to the refugium and then returns via an overflow to the main tank. Some of the pods and larval crustaceans will then be carried from the refugium into the sea horse tank in the water that overflows from the refuge. For this type of arrangement to work, the refugium must be slightly higher than the main tank. Shrimp are added to the refugium and within a few months they should start spawning and hatching eggs every few weeks. The larvae are then carried back to the main tank by the overflow, where they become a food source for your sea horses. Of course other life will also thrive in the refugium and it is not unusual for copepods, mysis and crab larvae to also be produced on a regular basis. The key to the refugium is to keep predators out of the system so that the smaller micro-crustacean population can thrive. You would need a fairly large and productive refugium to produce enough food to maintain even a pair of sea horses, so at best, a typical refugium can provide a nice source of supplemental live food; the basic daily diet still needs to be provided by you in the form of the frozen foods mentioned above." (Delbeek, November 2001, "Horse Forum," FAMA magazine).
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As you can see, Jason, in Delbeek’s description, a second smaller tank is used as the refugium and is positioned at a somewhat higher level than the main tank, plumbed so that it overflows into the main tank. With that type of refuge, it’s a simple matter to place an aquarium reflector with a fluorescent bulb atop the refugium to provide light for the Chaetomorpha, which can then be kept on a reverse photoperiod to the main tank in order to smooth out the daily variances in pH, dissolved oxygen levels, and so on…

When it comes to stocking your tank, sir, a yellow watchman goby makes a great companion for seahorses and scooter blennies also normally get along with them very well, with the exception of the occasional rogue specimen. But you are most definitely going to have to do without the Catalina goby, Jason. They are brilliant little fish with spectacular colors and are very gentle and docile, but they are temperate fish and there is simply no way you can keep a Catalina goby with tropical seahorses at 74°F-75°. The Catalina goby would be experiencing heat stress and it would eventually sicken and die. In the meantime, whatever affliction it developed after the heat stress compromised its immune system could be passed along to the rest of the residents in the tank as well. So scratch the Catalina goby off your wish list, sir.

If you are new to seahorses, sir, then I recommend you stick with a cleanup crew that consists of a nice assortment of snails, including both Nassarius snails to clean up meatier leftovers such as frozen Mysis, and a nice variety of herbivorous snails to graze on the algae and prevent nuisance algae from getting a toehold in your aquarium. I recommend that you stock the Nassarius snails at a density of one snail per 5 gallons, meaning that you would need 5-6 of the Nassarius snails for your 29-gallon tank. Likewise, the herbivorous snails should be stocked at a density of about one snail per gallon, meaning that you will need an assortment of 20-30 herbivorous snails for your setup when the biocube is fully stocked.

The herbivorous or grazing snails include Trochus snails, Astrea and Cerith snails, Nerites, red foot moon snails, Stomatellas, and Collonista snails. Try to distribute the appropriate number of snails for your particular tank fairly evenly between the smaller Astrea, Nerites, and Cerith snails, and then finish up by adding a few of the larger Trochus and red foot moon snails to make sure that your snail assortment will be able to handle all forms of algae that may appear in your aquarium.

In other words, Jason, I would cross the hermit crabs off your list and you should also eliminate the bumblebee snails, which are carnivores, and tend to supplement their diet with the beneficial herbivorous snails among your cleanup crew. Use Nassarius snails to scavenge the meatier leftovers instead – they are unsurpassed for that purpose! Go with an assortment of snails roughly following the breakdown I outlined above.

Your proposed list of corals looks fine, Jason. In general, soft corals are safe to use with seahorses and are good choices for a seahorse setup. The stony corals with small polyps can be used but the long polyp stony corals should generally be avoided.

Live seafans are very difficult to keep alive in the aquarium, Jason, and seahorse keepers usually have better luck using lifelike artificial gorgonians in place of the live gorgonians and sea whips or sea fans.

Since you are new to seahorses, Jason, the best thing you can do to make sure that your biocube is well prepared to provide ideal conditions for the seahorses would be to participate in the Ocean Rider seahorse training program for new seahorse keepers. This basic training is very informal yet quite comprehensive, and completely free of charge, sir. Ocean Rider provides the free training as a service to their customers and any other hobbyists who are interested in learning more about the care and keeping of seahorses. It’s a crash course on seahorse keeping consisting of 10 separate lessons covering the following subjects, and is conducted entirely via e-mail. There is no homework and there are no examinations or classes to attend or anything of that nature — just a lot of good, solid information on seahorses for you to read through and absorb as best you can, at your own speed, working at your computer from the comfort of your own home. The training course consists of a total of over 200 pages of text with more than 220 full color illustrations, broken down into 10 separate lessons.

If you would like to give the training program a try to make sure you are providing the best possible conditions for your ponies, Jason, just send me a brief e-mail off list ([email protected]) saying so and I will get you started out with the first lesson immediately. Since you are an experienced marine aquarist and your seahorse setup is already up and running, I would be happy to send you daily lessons so that you can complete the training program in as little as 10 days and be certified to order livestock thereafter.

Best wishes with all your fishes (and invertebrates), Jason!

Pete Giwojna

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