Live rock or not?

Dear Alex & Mark:

The use of live rock in a seahorse setup is strictly optional, not mandatory by any means. Live rock provides many benefits for a marine aquarium such as increased stability, denitrification to keep the nitrate levels nice and low, and providing shelter and sustenance for a large population of copepods and amphipods (natural seahorse fodder). Live rock can also be very attractive when it is covered by pink or purple coralline algae and other colorful encrusting organisms. For these reasons, some hobbyists prefer to use live rock as the primary means of biological filtration in their seahorse setups, in which case they may use up to 1-2 pounds of live rock per gallon.

Other seahorse keepers avoid live rock like the plague and will tolerate no live rock whatsoever in their seahorse setups. This is usually done in order to assure that unwanted hitchhikers that could present a risk to the ponies, such as mantis shrimp, Aiptasia rock anemones, and bristleworms or fireworms, don’t enter the aquarium along with the live rock. Or they may be keeping colorful seahorses and therefore avoid masses of drab live rock (brown or gray or black) so that it does not dominate the aquarium and cause their ponies to darken in order to better blend in with the relatively drab background provided by the live rock.

So the short answer to your question is that seahorses can be kept successfully in an aquarium with no live rock whatsoever, providing the tank has other means of adequate biological filtration, or seahorses can be kept very successfully in an aquarium that is chock full of live rock. Either method can work very well if the aquarium is properly filtered and maintained, so feel free to follow your own preferences in that regard.

However, the long answer to your question is not so simple, Mark and Alex. For example, in many cases, my preferred setup for seahorses is a "Seahorse-Only with-Live-Rock" (SHOWLR) system, and this is what I usually advise home hobbyists in that regard:

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Live Rock

The one indispensable part of a SHOWLR system is the foundation of live rock. The live rock is the living, breathing, heart and soul of the system, which provides the bulk of the biological filtration as well as some denitrification ability and shelter and habitat for countless critters and microfauna. The porous interior of the rock supports large populations of the beneficial oxygen-loving Nitrosomonas and Nitrobacter bacteria that breakdown deadly ammonia and nitrite into less toxic substances (primarily nitrate). Deeper inside the live rock, where oxygen levels are nil, anaerobic denitrifying bacteria take hold and complete the nitrogen cycle, breaking down nitrate into harmless nitrogen. This helps keep the nitrate levels in the seahorse tank low. As a result, live rock is superior to most other forms of biofiltration, which lack this final anaerobic step and cannot carry out denitrification. This makes live rock doubly good at maintaining optimum water quality.

Equally important, the rockwork provides cover for the seahorses. By this, I mean the rock allows the seahorses to hide and conceal themselves completely whenever they feel the need. Seahorses are shy, secretive creatures that rely on camouflage as their primary means of protection, and if they feel too exposed and vulnerable, it can be stressful for them.

How much live rock is needed for a seahorse tank? Well, that depends on one’s personal preferences and the filtration system in the aquarium. For example, many reef systems rely on live rock and live sand as the only means of biological filtration, along with power heads to provide good water circulation and a protein skimmer for supplemental filtration. In a system like that, where the live rock serves as the primary biofilter, as much as 1-2 pounds of live rock per gallon is needed to do the job. That amount of live rock will provide adequate levels of both nitrification and denitrification for the tank, and that is the maximum amount of live rock anyone would ever consider installing in their seahorse tank. Most seahorse setups need no more than 1 pound of live rock per gallon at the most.

However, if you will have an additional means of biological filtration on the aquarium, then you won’t need nearly that much live rock and you can get by with a small fraction of that amount very nicely. Most seahorse keepers prefer to use an external filter with biological filtration ability along with just enough live rock to provide their tank with stability due to the additional biofiltration and shelter it provides, and for decorative purposes. That way they get many of the benefits the live rock provides but the tank remains less cluttered with more swimming space for the seahorses.

In a case like that, the live rock complements the biofilter due to it’s ability to provide denitrification (i.e., the conversion of nitrate to nitrogen gas, which leaves the aquarium) and complete the nitrogen cycle. This helps to keep the nitrates low and the supplemental biological filtration the live rock provides gives the aquarium greater stability and a bigger margin for error.

So in an aquarium that has an external filter which provides efficient biological filtration (e.g., a wet/dry trickle filter, bio wheel, or canister filter or hang-non-the-back filter with bioballs or other biological filtration media), there is no minimum amount of live rock that must be used. Such an aquarium has adequate biofiltration ability without the need for live rock. It can therefore include many interesting formations of live rock for shelter and decorative purposes, just a little live rock to provide additional stability and to help keep the nitrates under control, or even no live rock at all. Whatever amount the aquarist prefers is just fine when the live rock is not providing the biological filtration. In such cases, 1 pound of live rock per 10 gallons should suffice.

But the stability and denitrification ability provided by the live rock, and the diversity of life it supports, are always an asset for any aquarium, so nowadays most seahorse tanks include at least some live rock. The abundant copepods and amphipods and other meiofauna that come to populate the live rock provide tasty treats for the seahorses between meals, which our galloping gourmets always appreciate.

To take advantage of the benefits provided by live rock, you can simply select the precured live rock you find most attractive at your LFS and add enough of it to create interesting rock formations that are aesthetically pleasing to your eye. Use enough rock to create some interesting caves, arches, ledges and overhangs, but make sure that the rockwork is very well secured and anchored solidly in place so that there is no instability or danger that the rock formations could collapse.

Despite its beauty, natural appearance and the many benefits it provides, some hobbyists avoid live rock like the plague for fear that they may introduce harmful pests to their aquarium along with the live rock. This is a valid concern since potentially harmful hitchhikers like mantis shrimp, fireworms, aggressive crabs, hydroids and Aiptasia rock anemones are very often unseen and unwanted tenants of live rock. They insinuate themselves throughout the live rock in nooks and crannies, and multitudes of these squatters may have taken up housekeeping in a good-sized piece of rock unbeknownst to the unsuspecting aquarist. They conceal themselves within the labyrinth of rock and often escape even the closest scrutiny undetected.

But with a little care this is one time when aquarists can have their cake and eat it too. There are a number of ways to take advantage of all the benefits live rock provides without risking unleashing an epidemic of tenacious rock anemones or turning Jack-the-Ripper loose in your tank reincarnated in the form of a thumb-splitting Stomatopod.

By and large, bristleworms are beneficial scavengers and sand sifters unless their numbers get out of hand, so a good option for many seahorse keepers is to keep the Aiptasia and bristleworm population in check using some means of biological control. Peppermint Shrimp (Lysmata wurdemanni) love to dine on Aiptasia rock anemones and several of these attractive shrimp will do a fine job of eradicating them from the aquarium. Certain nudibranchs (Berghia sp.) also feed on Aiptasia. Likewise, small Arrow Crabs (Stenorhynchus sp.) will keep the bristleworm population at a manageable number. Any mantis shrimp or aggressive crabs that happen to slip by are generally fairly easy to trap and remove, and commercially made traps are available for that very purpose.

Treating the live rock with a hypersaline dip (or a hyposaline dip) is another excellent technique for ridding it of unwanted pests. This method doesn’t kill the critters outright but merely drives them out of the rockwork so you can selectively cull through them. Another advantage of this method is that leaves all the desirable life on the rocks intact and unharmed.

To use this technique, simply place your newly arrived live rock in an inert container filled with saltwater at a specific gravity of at least 1.045 to 1.050 for several minutes before you introduce it to the aquarium. The saltier the water, the shorter the length of time you need to soak the live rock and the more effective it will be in driving out unwanted hitchhikers. Invertebrates cannot tolerate rapid changes in salinity, so all the mobile inverts in the rock will immediately abandon there hidey-holes and bale out of the rock like rats deserting a sinking ship. After several minutes in this extra-salty bath, the evacuation will be complete, and you can remove the now pest-free live rock and sort your catch. Cull the invertebrates left behind in dipping container, discarding the pests you don’t want while retrieving any of the refugees you might like to add to your system. Several minutes in the hypersalinity is usually enough to drive out all the active invertebrates such as mantis shrimp (Stomatopods), crabs, and assorted worms of every description, yet this brief period of immersion will not harm encrusting organisms or sessile life.

Some hobbyists prefer a low salinity bath to debug their live rock, rather than a hypersaline dip, and some will even briefly immerse the live rock in freshwater to drive out unwanted hitchhikers. This is also an effective technique for eliminating pests from the live rock, but using freshwater may impair the beneficial nitrifying bacteria within the porous live rock if you overdo it, and the organisms that are driven out of the live rock will not survive in freshwater for any length of time, so it’s difficult to cull through them and recover any desirable microfauna, such as copepods and amphipods. Freshwater immersion can also be harsh on desirable encrusting organisms and sessile lifeforms.

The best way to obtain live rock is from an aquarium store in your area that caters to reef keepers. They will have pre-cured live rock available and you can handpick interesting rock formations that are heavily encrusted with pinkish-purple coralline algae for your aquarium. That will also save you the cost of having the live rock shipped to you, which can be considerable because of the weight of the rocks.

Seahorse keepers who want brightly colored seahorses will often choose to confine the live rock to their aquarium sump or refugium, rather than the main tank, particularly if they are unable to obtain colorful live rock with lots of coralline algae. The reason for this is that an aquarium with lots of ordinary brownish live rock can sometimes have an adverse effect on the appearance of ponies with vivid coloration. As we all know, our seagoing stallions will often change coloration in order to better blend in with their background, and that means that they may adopt earth tones in an aquarium that is dominated by drab live rock. Although that’s not a concern with dark colored seahorses, it would be a shame to purchase a bright yellow or orange or red seahorse only to have it assume a brown or beige or sandy or grayish background coloration that matches the live rock. Placing the live rock in the sump or refugium instead of the display tank eliminates this possibility, yet still allows the aquarium to benefit from the greater stability, enhanced biological filtration, and denitrification ability (which helps keep nitrates nice and low) provided by the live rock.

And, of course, situating the live rock in a refugium or sump connected to the main tank also eliminates the possibility of unwanted pests entering the aquarium has hitchhikers on the live rock. So that’s a convenient way to obtain all of the benefits live rock provides without the risk that bristleworms, Aiptasia rock anemones, mantis shrimp or rock crabs or pistol shrimp will gain entry into your seahorse tank along with the live rock. Many seahorse keepers who are worried about such undesirable pests therefore confine their live rock to a sump or refugium, or start out with dried rock that is completely free of such hitchhikers instead.

Pest-Free Dry Rock

Another good option, which is the safest and easiest procedure for most home hobbyists (especially those new to the hobby), is to start out with "dead" foundation rock instead of live rock. This dead or dry foundation rock is considerably cheaper than colorful live rock and is, of course, entirely free of undesirable pests and unwanted hitchhikers. But it will quickly enough become alive once it’s placed in the aquarium as it’s overgrown by algae and inhabited by copepods, amphipods and myriad microfauna. And over time the porous dead/foundation rock will become inhabited by a thriving population of nitrifying bacteria, giving it biofiltration ability. Eventually the oxygen-deprived interior of the "dead" rock will be populated by aerobic denitrifying bacteria, which convert nitrate to nitrogen gas, thereby helping to keep the nitrate levels in the aquarium under control.

By this point, the foundation rock will be very much alive and can provide all the benefits of live rock with none of the risks. The inert foundation rock looks completely natural when surrounded by living, growing macroalgae, especially when it becomes encrusted by microalgae or coralline algae, as the case may be.

The drawback to this approach is that it takes considerably longer for a new marine aquarium to cycle from scratch using dry rock than it does with live rock, and you must "seed" the tank with beneficial nitrifying bacteria from another clean source in order to start the cycling process. But the advantage of using dead foundation rock is the cheaper cost and, above all, the fact that it completely eliminates unwanted hitchhikers such as Aiptasia rock anemones, bristleworms, mantis shrimp, hydroids, and rock crabs. If they are patient, many home hobbyists feel the advantages outweigh the drawbacks.

One good source for such dry foundation rock is Macro Rocks, which offers dead, dried ocean rock in a number of interesting formations and a wide variety of types (Florida, Fiji, Tonga, etc.). They offer many beautiful, unique and intricate formations of dried ocean rock that would be an asset to any seahorse setup. Best of all, you can even purchase the Macro Rocks precycled and carrying a full complement of beneficial nitrifying bacteria, which allows you to cycle a new aquarium using the Macro Rocks as fast as an aquarium with live rock.

Macro Rocks are available online at the following website:

http://www.marcorocks.com/index.asp?PageAction=VIEWCATS&Category=14
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Okay, Alex and Mark, that’s the quick rundown on live rock. If you have never worked with live rock before, or you cannot afford the expense, are you are concerned about introducing unwanted pests, feel free to omit the live rock from your seahorse setup. Just be prepared to take other measures to keep your nitrate levels in the desired range, such as more frequent partial water changes or maintaining a lush bed of macroalgae that you harvest regularly.

Best of luck with your new seahorse setup, fellas! Have you given any thought to participating in the free Ocean Rider seahorse training course to make sure that your new aquarium is optimized to provide ideal conditions for the ponies? If you want to give it a try, just send me a brief e-mail with your full names to the following address, and I will get you started out with the first lesson right away: [email protected]

Good luck!

Happy Trails!
Pete Giwojna