Filtration recommendation please

Dear gilraen:

It sounds like you’ve already got a pretty good idea of the type of filtration that would be appropriate for a 55-gallon seahorse tank, but I would be happy to share my thoughts on the matter with you.

First of all, let me just say that a 55-gallon aquarium is a good choice for a seahorse tank. It should be at least 20 inches tall (the taller the better), which is very important for seahorses in order to protect them from depth-related conditions such as certain forms of gas bubble disease and to provide the vertical swimming space they need for mating and the exchange of eggs. And your 55-gallons system will have sufficient water volume to provide stability and a good margin for error.

I like your lighting system as well. 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before the daylight tubes and stay on after the daylights go off, thereby providing a simulated dusk and dawn (Giwojna, unpublished text).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 I find that maintaining a natural cycle this way aids reproduction (Giwojna, unpublished text).

Basically, 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The resulting dusk and dawn facilitate courtship and help the seahorses maintain a natural reproductive cycle (Giwojna, unpublished text).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 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.

The moonlights are also a nice touch for a seahorse tank. Seahorses have a sort of corrugated retina densely packed with rods, which gives them excellent visual acuity under low light levels, and a few species (e.g., Hippocampus comes and H. ingens) are even said to have adapted nocturnal habits in some areas in response to heavy fishing pressure. So they may well appreciate the moon lighting and respond positively to it. Mating in some seahorses with pelagic fry is synchronized to coincide with the highest tides (hence moon phases), so the moon lights make even help stimulate breeding as they are said to do with some types of corals.

As far as the filtration system goes, I like a wet/dry trickle filter used in conjunction with live rock. The wet/dry trickle filter will provide water movement and wonderful nitrification to control ammonia and nitrites, as well as increasing the carrying capacity of the aquarium, whereas the anaerobic bacteria within the porous interior of the live rock will provide denitrification to complete the nitrogen cycle and help to keep the nitrates nice and low.

Wet/dry trickle filters are top-of-the-line units that feature a thin film of water trickling over filter media with an ultra-large surface area, thereby allowing maximum air-water contact. This provides excellent oxygenation with efficient offgassing, which is very important for seahorses. It helps keep dissolved oxygen levels high, CO2 low, and effectively prevents gas supersaturation, which can sometimes contribute to serious problems for our aquatic equines. As a added benefit, wet/dry trickle filters can also provide remarkable biological filtration, which can give you a real nice edge by further increasing your carrying capacity and boosting your margin for error accordingly.

And a protein skimmer is ordinarily a a great addition to a seahorse system, particularly if you have a sump and/or a wet/dry trickle filter to guard against the possibility of gas supersaturation. Although seahorses can certainly be kept successfully without the use of a protein skimmer, I recommend including a good skimmer for best results. As a rule, seahorses are messy feeders, particularly when scarfing down enriched frozen Mysis. Ample evidence of this is revealed every time they scarf one up. As they snick up a shrimp with their slurp-gun snouts, water is passed over their gills and expelled forcibly (it is this very process that generates the powerful suction they use to slurp up their prey). As the jet of water is ejected through their gills, it carries a cloud of macerated particles and debris with it. It is a startling sight the first time you observe this phenomenon, for it brings a fire-breathing dragon to mind. As one young hobbyist matter-of-factly described it, "My seahorse blows smoke out of its ears when he eats." I’ll be darned if that’s not exactly what it looks like, too!

The majority of the undesirable metabolites, organic wastes and excess nutrients that accumulate in our aquariums and degrade water quality are "surface-active," meaning they are attracted to and collect near the surface of a gas-liquid interface (Fenner, 2003). Skimmers take advantage of this fact by using a column of very fine air bubbles mixed with aquarium water to trap dissolved organics and remove them from our systems. This air-water mixture is lighter than the surrounding aquarium and rises up the column of the skimmer until the foam eventually spills into a special collection cup atop the skimmer, which can be removed and emptied as needed. Proteins and other organic molecules, waste products, uneaten food and excess nutrients, and a host of other undesirable compounds stick to the surface of the bubbles and are carried away along with the foam and removed from the aquarium (Fenner, 2003a). As a result of this process, these purification devices are typically known as foam separators, foam fractionators, air-strippers, or simply protein skimmers.

In my experience, nothing improves water quality like a good protein skimmer. They provides many benefits for a seahorse setup, including efficient nutrient export, reducing the effective bioload, and increasing both the Redox potential and dissolved oxygen levels in the water (Fenner, 2003a). They do a tremendous job of removing excess organics from the aquarium, including phenols, albumin, dissolved organic acids, and chromophoric (color causing) compounds (Fenner, 2003a). Their ability to remove dissolved wastes BEFORE they have a chance to break down and degrade water quality makes them indispensable for controlling nuisance algae. A good protein skimmer is an invaluable piece of equipment for keeping your nitrates low and your water quality high when feeding a whole herd of these sloppy eaters in a closed-system aquarium.

So all in all I would say the filtration system you have in mind for your 55-gallon aquarium should work very well for seahorses. The only other thing I could suggest is that you might want to consider having your 55-gallon aquarium drilled so that you could equip it with a sump.

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. This eliminates the possibility of heater burns and prevents your seahorses from adopting a siphon tube or heater cord or other piece of apparatus as a favorite perch instead of the colorful hitching posts you have provided for them. (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 or other macroalgae (Gracilaria, Chaetomorpha, etc.). 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 macroalgae 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. (Other macroalgae require a period of darkness in order to thrive, but if you will be using Caulerpa, it can even be illuminated 24 hours a day around the clock in order to accomplish the same thing.) 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.

Best of luck converting your 55-gallon aquarium to a seahorse tank, gilraen!

Happy Trails!
Pete Giwojna