A 100 gallon aquarium would make a fine home for a herd of seahorses! As an experienced marine aquarist, you have a good background to become a successful seahorse keeper. I’ll try my best to answer your questions one by one below:
A thin layer of live sand, preferably black, is the ideal substrate for a SHOWLR tank. It is bioactive, aesthetically pleasing, and is a fine-grained sand well suited for the various snails that form an essential part of the cleanup crew for a seahorse tank. I find the dark color shows off my seahorses and macroalgae to great effect and enhances the appearance of tank in general. (As long as it’s fine enough I’ve never had any problems with seahorses "snicking" up sand in the aquarium. They will do so on occasion when feeding off the bottom, but never have any difficulty at all expelling it again as long as it’s fine grained.)
The depth of a shallow sand bed like this is a crucial factor. Too deep, and you risk anaerobic dead spots where deadly hydrogen sulfide gas can form. Too shallow, and there will be less surface area to support beneficial nitrifying bacteria and Nassarius snails and other beneficial burrowers may feel vulnerable and exposed. A bed of live sand 3/4-inch to 1-inch deep is just right for the main tank. A properly layered Deep Live Sand Bed (DLSB) 3-6 inches deep with a full complement of sand shifters also works well with seahorses, but is best confined to a sump (see discussion below) rather than the display tank due to the seahorse’s heavy waste production. In other words, you can minimize the buildup of detritus in the DLSB by installing it in your sump rather than the main tank.
Lighting the Seahorse Tank
When it comes to lighting, seahorses do not have any special requirements other than the fact that most species prefer low to moderate light levels rather than excessively bright light. They have a corrugated retina especially rich in rods, which gives them excellent visual acuity under twilight conditions and low light levels in general. But this does not mean that they shun bright light, just that they appreciate shady retreats as well as brightly illuminated areas.
In actual practice, seahorses will do well under any type of lighting you prefer — from metal halides to power compacts or VHO lighting to daylight fluorescent tubes to ambient room light — providing well-shaded areas are available to them and overheating does not become a problem.
Hippocampus is often displayed under metal halide lighting at public aquaria (Seahorse Husbandry Manual, 2002), and I know many reef keepers who keep seahorses in their systems under metal halides. Often the reefers will keep the coral and inverts that require strong light at one end of the tank, where the metal halides are concentrated, and keep the other of the tank shaded to accommodate the seahorses, reserved for corals that don’t need high-intensity lights. Or they will use pendants as spotlights, focusing the metal halides on the areas with corals that require the strongest light, and leave other areas of the reef less brightly illuminated. This can produce a very attractive affect similar to sunbeams filtering through broken clouds. If need be, you can also provide shaded areas by positioning sections of aluminum foil atop your aquarium that are the right size and shape to cast shadows where you want them below. Basically, you can’t go wrong with seahorses when it comes to lighting as long as you provide some dimly lit areas they can retreat to when they would like to get away from the light and some brightly lit areas they can move to when then want to bask in the light.
In fact, my primary concern when using metal halides on a seahorse tank is the water temperature rather than the intensity of the light. Metal halides throw off a lot of heat and most of the tropical seahorses do best at temperatures of around 73°F-75°F; so avoiding temperature spikes above 80°F is very important.
Personally, I like to provide my seahorses with a natural day/night period that includes twilight periods at "sunrise" and "sunset." To accomplish this, I like the power compact (PC) light fixtures that include two tubes — one actinic and one daylight fluorescent — with dual ballasts so that each ballast can be placed on a separate automatic timer. I like to have the bluish actinic come on before the daylight tubes and stay on after the daylights go off, thereby providing a simulated dusk and dawn (Giwojna, unpublished text). This is important for seahorses since they conduct most of their courting and breeding in the early morning hours under twilight conditions. It’s a neat effect and fish and invertebrates can then anticipate "lights out" rather than being plunged into total darkness at night or suddenly thrust into bright light in the morning. I also adjust the timers to lengthen or shorten the daylight periods in accordance with the changing seasons. I find that maintaining a natural cycle this way aids reproduction (Giwojna, unpublished text).
In short, I find PC lighting to be a good compromise for a seahorse system. Power compacts provide plenty of light for macroalgae or the seahorse-safe soft corals in a modified reef system without being too bright or generating too much heat, and the dual ballast system allows for a natural day/night rhythm that changes with the seasons. The resulting dusk and dawn facilitate courtship and help the seahorses maintain a natural reproductive cycle (Giwojna, unpublished text).
For all intents and purposes, you really can’t go wrong no matter what lighting system you chose as long as you provide both shaded areas where your seahorses can escape from the light altogether and well-lit areas where they can bathe in bright light as they please. You will find your seahorses will move into and out of the light often, seeking the comfort level that suits them at the moment.
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)."
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 (like your 100 gallon setup) 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.
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.
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.
As long as your seahorses aren’t getting buffeted around by the currents, aren’t spilling eggs during the copulatory rise, and aren’t having difficulty targeting their prey and eating, there’s no such thing as too much water movement. 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.
There are many advantages to adding a sump to your seahorse setup. For starters, it increases the overall water volume of your system with all the benefits that implies. A good-sized sump can easily double your carrying capacity, increasing your safety margin accordingly. It makes an ideal place to put a protein skimmer, heater(s), air stones, and other equipment so they don’t have to be hidden in the display tank. (A well-designed sump does a great job of trapping and eliminating the microbubbles emitted from skimmers and preventing them from entering the aquarium, and provides an excellent way of increasing the aeration/oxygenation, which is so important for a seahorse setup.) It’s the perfect place to perform additional mechanical and chemical filtration, tailoring the filter media to meet ones exact needs, or to add a calcium or nitrate reactor or even a Deep Live Sand Bed (DLSB) to your seahorse setup. Because the sump is a large body of water separated from the aquarium itself, it facilitates water changes, dosing supplements, adding top-off water to the tank and other maintenance tasks, all of which can be carried out in the sump without disturbing the main tank or stressing its inhabitants. Entire sections of the mechanical filtration can be cleaned at one time without affecting your primary biofilter, and water changes can be performed gradually without causing stress to the fish or invertebrates. A sump/refugium can also be used to grow a lush bed of macroalgae using a reverse lighting cycle to stabilize the pH and absorb wastes.
To take advantage of these benefits, I suggest adding a two-chambered sump to your tank. This can be accomplished by installing a perforated tank divider across the width of the sump, thereby separating it into two isolated compartments. One side accommodates all of your equipment (in-sump skimmer, return pump, heaters, titanium grounding probe, UV sterilizer, etc.) while the other side can be used to establish a deep live sand bed (DLSB) with plenty of Caulerpa. The DLSB/Caulerpa side serves as a refugium and will soon become populated with countless critters (copepods, Gammarus and other amphipods, larval crustaceans, etc.). With the Caulerpa acting as an algal filter and the anaerobic layers of DLSB providing denitrification, the aquarist never need be concerned about nitrates or nuisance algae with this type of sump/refugium.
In addition, the biological refugium/sump can be maintained on an opposite light cycle to the main tank to offset the daily fluctuations in pH, photosynthesis, dissolved oxygen/carbon dioxide, and redox levels that otherwise occur in the aquarium. Daily variances in chemical, physical and biological phenomena are a fact of life in aquaria, linked to the light and dark cycles and the diurnal rhythms of captive aquatic systems. As one example, the pH of aquarium water typically peaks after the lights have been on all day at a maximum of perhaps 8.4, only to drop to low of below 8.0 overnight. This is related to photosynthesis and the fact that zooanthellae and green plants consume CO2 and produce O2 when there is adequate light, but in essence reverse that process in the dark, consuming O2 and giving off CO2. Redox levels, available calcium and other water quality parameters are affected in similar ways. Needless to say, these variations are far greater is a small, closed-system aquarium than they are in the ocean, so it’s beneficial to minimize such fluctuations by reversing the photoperiod in the main display and the sump/refugium. This is easily accomplished by timing the lighting in the sump so that the bed of macroalgae is illuminated after dark when the lights on the display tank are off, and vice versa. Just use alternating timers on the main tank and the refugium tank so that when one is on, the other is off. Voila! Just like that the roller coaster ride is over: no more daily fluctuations in pH or highs and lows in calcium levels, oxygen minima, or peaks and valleys in redox potential.
Because it is separate from the main system yet shares the same water, the sump/refugium can also be used as a nifty acclimation tank for new arrivals or a handy isolation tank for separating incompatible specimens. For seahorse keepers, the refugium compartment of a divided sump or dual chamber sump makes an ideal grow-out tank for juvenile seahorses that have outgrown their nurseries but are still too small to be kept in the main tank. A dual-chamber sump is a very versatile design that lends itself to multiple purposes. Use your imagination.
Whatever type of sump you decide to install, Mort, be sure to equip it with an efficient in-sump protein skimmer and a titanium grounding probe to eliminate stray voltage. An ultraviolet sterilizer is also a good investment for the seahorse keeper, as discussed below, and could be easily installed in your sump.
Although it does not improve water quality to nearly the same degree as an ozonizer used in conjunction with a protein skimmer, UV radiation in the proper range (295-400 nanometers) is known to help oxidize phosphates, metabolites, organic molecules and nitrogenous compounds through the incidental production of ozone (Fenner, 2003a).
The primary benefits UV sterilization provides, however, are disease reduction and the reduction of nuisance algae. Ultraviolet radiation can be very effective in reducing free-floating algae, bacteria and microbes in general, certain parasites while in the free-swimming stages of development, and other suspended microscopic organisms (Fenner, 2003a). Seahorses are prone to a number of serious bacterial problems such as Vibriosis, and a properly installed and maintained UV sterilizer can be invaluable in reducing the incidence and spread of such infections. When properly used, UV sterilization can reduce microbial levels in the aquarium to the low levels normally found in the wild or below (Fenner, 2003a).
For best results, the UV sterilizer must be properly sized, operated, and maintained. In order to provide a good kill rate per pass, the effective dwell time (the length of time the water is exposed to UV radiation while passing through the sterilizer) should be maintained at or above roughly twenty gallons per hour flow per watt of UV (Fenner, 2003a). This sounds complicated, but selecting the right sterilizer for your needs is actually very easy. Every manufacturer provides guidelines to help the hobbyist choose a unit and a pump that provide the proper wattage, flow rate and exposure time for any given application.
To assure efficient transmission of the proper wavelengths, sleeves (i.e., the quartz jacket that shields the lamp) must be kept clean and UV bulbs must be replaced at regular intervals. Equally important, the aquarium water should be filtered before it passes through the sterilizer. For maximum efficiency, make the UV sterilizer the final component of an in-line filtration system, so that the water has already passed through your mechanical, biological and chemical filtration media before it flows through the sterilizer (Fenner, 2003a). Do not operate your UV sterilizer during the break-in period when a new aquarium is being cycled and the biological filtration is becoming established. It is counterproductive to reduce microbe levels and nutrient levels when the aquarium is cycling.
Ultraviolet sterilizers are not necessary for maintaining seahorses, but nowadays I would not attempt to keep wild-caught seahorses without one. Hardy, disease-resistant farmed-raised seahorses can do just fine without them, and reefers often frown on UV because it reduces the population of microscopic planktonic organisms filter-feeding invertebrates require. But in my opinion a UV sterilizer makes a very useful addition to the filtration system of the average seahorse setup. The fish farms and aquaculture facilities that raise captive-bred seahorses employ UV radiation in their nurseries and grow-out tanks, and there is no reason the home hobbyist should not take advantage of this technology as well.
The most important thing to remember when selecting seahorses for your new aquarium is to avoid while-caught seahorses at all costs! You can’t go wrong captive-bred-and-raised Mustangs (Hippocampus erectus) as your first seahorses for reasons that will be discussed in more detail in the discussion threads listed below.
There have been a few other threads on the Ocean Rider Club discussion board at seahorse.com from hobbyists who were just starting out with seahorses that you should also find to be of interest. They discuss setting up an ideal system for seahorses, filtration, feeding, lighting, circulation, the best seahorses for beginners, and so on. I’ve provided links to those discussions for you below, Mort, so please check them out when you have a chance. I think they will answer many of your questions about keeping seahorses:
Re:Hello, newbie here! – O http://www.seahorse.com/option,com_simpleboard/Itemid,144/func,view/id,1004/catid,2/
Re: Guidance on Keeping Seahorses:
Re: New to seahorses and I have lots of questions!
Re: Tank set-up advice
Re:New with lots of questions 🙂
Please let us know if you have any other questions that haven’t been covered in those previous discussions, sir!
Best of luck with your new seahorse setup, Mort!