starting from the basics

Dear lilypad:

A reverse osmosis unit is much like a protein skimmer — an optional piece of equipment for the seahorse keeper rather than a prerequisite, but highly recommended in most cases. In many areas, the municipal water supply yields water that contains low levels of amines, nitrates, and phosphates, and if you are located in such an area, then an RO/DI unit is very desirable to avoid problems with nuisance algae and to maintain optimum water quality.

Your present RO unit is a great improvement over unfiltered well water, but if possible, it’s an excellent idea to get a deionization (DI) filter for it as well. It won’t add to the total cost that much and it further improves the purity of the resulting water. Adding the deionization filter will assure that the total dissolved solids (TDS) of the filtered water will be zero.

If you’re going to be maintaining a fish only aquarium, then your present RO water (or even detoxified tap water) will usually suffice. But if you want to maintain live corals in the aquarium along with the seahorses, then RO/DI water will usually produce the best results.

Regarding the lighting, lilypad, my primary concerns with metal halides are overheating, an adverse affect on brightly colored seahorses (which often darken in response to the high-intensity lighting), and the fact that seahorses may go into hiding if the lighting is excessively bright. In your instance, it sounds like the metal halide fixture with the built-in cooling fans does not have a significant effect on the water temperature, which would eliminate overheating as a concern. Likewise, if you are going to be purchasing Mustangs (Hippocampus erectus), which primarily exhibit the typical brown or black coloration characteristic of wild erectus, then the metal halides will not detract from their coloration either, as it might for Sunbursts or colorful H. reidi seahorses.

That leaves only the fact that seahorses don’t like excessively bright lighting and may go into hiding, seeking sheltered spots and shady areas within the rockwork if the lighting is too intense for their liking. That’s something that you can control. Perhaps you could keep one end of the aquarium brightly illuminated with metal halides, and leave the other end of the aquarium well shaded, reserved for the low-light corals. That would allow the seahorses a shady area they can retreat to when they would like to get out of the blight light.

So, if you can provide low light areas for the Mustangs and the metal halide lighting does not raise the water temperature significantly, I see no reason not to use the metal halide fixtures and leave them on as you normally would.

However, if your aquarium package has metal halide lighting, then it’s probably designed with reef keepers in mind. If that’s the case, it will probably also have strong water pumps that produce the vigorous water currents and brisk circulation that many live corals require in order to thrive, and that could be another cause for concern. If you can tell me what size the aquarium is (i.e., it’s water volume) and how many gallons per hour the pump and filter put out, we can determine if the water flow could be problematic for the seahorses or not.

Here is some additional information regarding compatible live corals that do well with seahorses, and how to modify reef-ready tanks to make them safe for seahorses which may be helpful in your future planning, lilypad:

Seahorse-Proofing the Reef Tank

When designing a reef tank that will include seahorses, one must anticipate the different ways they might be injured in such a setup and then take precautions to prevent them from coming to harm. The process of rendering your reef system seahorse safe is much like the measures new parents take to childproof their house when they are expecting their first child. Intake tubes for the filters should be shielded, siphon tubes should be equipped with filter baskets or screens, and so on…

For instance, when powerful water movement is combined with overflows, there is a risk that seahorses could become pinned against an overflow or even go over it (Delbeek, Oct. 2001). Therefore, in the seahorse reef, overflows must be baffled and/or screened off, or the water flow should be adjusted sufficiently to prevent that from happening.

Likewise, although seahorses have no problem with strong currents in the wild, in the confines of aquarium, it is possible for them to come in contact with stinging corals if they are struck by a sudden powerful wave or surge, or are overwhelmed by a strong, unexpected current (Delbeek, Oct. 2001). The hobbyist needs to take this into consideration when placing water returns and corals in the seahorse reef (Delbeek, Oct. 2001). If possible, 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.

One good way to accommodate both the needs of corals that prefer brisk currents and the seahorse’s need for slack-water retreats is to create tall rock formations a foot or two down current from the strongest water flows to intercept and deflect or divert that strong flow of water, creating eddies and slack-water zones where there is relatively little water movement down current. Seahorses will hold in these low flow areas when they want to move away from the current, so it’s a good idea to position convenient hitching posts in the lee or down-current side of such formations..

Another excellent way to accomplish the same thing is to use small powerheads to create and direct current wherever needed. A properly positioned powerhead can thus bathe your prized Acropora formations in a brisk water stream precisely without generating too much water movement elsewhere in the aquarium. Just be aware that powerheads can become death traps for seahorses if their intakes are not properly shielded or screened off, and take the necessary precautions (Delbeek, Oct. 2001). Carefully conceal the intakes amidst the rockwork where they will be completely inaccessible to seahorses, otherwise shield them, or screen them off with a sponge prefilter.

In short, the hobbyist who wants to keep seahorses in a reef system must be willing to make some concessions and modifications to accommodate their special needs nonetheless. For example, the reef keeper must be willing to limit himself to corals and invertebrates that meet the following criteria:

1) Avoid any stinging animals with powerful nematocysts. This means fire corals (Millepora spp.) and anemones should be excluded from the seahorse reef, and any corals with polyps that feel sticky to the touch should be used with discretion and only after careful planning. When a seahorse brushes up against them or attempts to perch on them, the nematocysts or stinging cells of these animals can penetrate the seahorse’s skin and damage its integument. Needless to say, this causes pain and discomfort and can leave the seahorse vulnerable to secondary bacterial and fungal infections, which may take hold at the site of injury. Short polyped stony (SPS) corals are generally fine, but large polyped stony (LPS) corals should be regarded with caution, as discussed in more detail below.

2) Water movement and circulation must be managed as previously described. Corals that require powerful surge or overly strong water currents could overtax the limited swimming ability of Hippocampus unless slack water areas the seahorses can retreat to when needed are also provided.

3) The corals must be able to withstand being used as hitching posts by the seahorses from time to time; that is, they cannot be so delicate that having a seahorse’s grasping tail anchored around them could cause them any harm. For instance, soft corals may retract their polyps when a seahorse perches on them. This can be harmful to their health if it becomes a chronic problem, because many corals rely on their polyps to absorb light and convert it to energy via photosynthesis. Be sure to watch any soft corals and hermatypic corals to make sure they are not closed up for extended periods. Normally, they adjust to the seahorses’ presence and unwelcome attention after a while, and remain contracted only briefly after each contact. After repeated exposures to grasping tails, each such incident elicits a weaker response, so they tend to extend their polyps sooner and sooner after being disturbed (Delbeek, Oct. 2001).

4) Avoid Tridacna clams and similar bivalve mollusks. Sooner or later a seahorse will perch on them with its tail between the valves and the clam’s powerful adductor muscle will clamp down on it like a vise. At best this will be a very stressful experience for the unfortunate seahorse, since it can be the devil’s own business trying to persuade the stubborn mollusk to release its struggling victim! At worst, it can result in serious injury or permanent damage to the seahorses tail (Giwojna, unpublished text).

5) Beware of unwanted hitchhikers that may have come in on your live rock unbeknownst to you and which can harm seahorses, such as fireworms, mantis shrimp, or Aptasia rock anemones. When setting up a reef system for seahorses, it’s a wise precaution to pre-treat your live rock with a hypersaline bath to drive out such pests beforehand because they can be very difficult to remove or eradicate once they make themselves at home in your aquarium (Giwojna, unpublished text).

As long as the specimens you are considering for your seahorse reef satisfy these requirements, anything goes! Some of the good and bad candidates for such a reef system are discussed below:

Seahorse-Safe Corals

Soft corals have very little stinging ability and generally make good choices for a modified mini reef that will include seahorses (Delbeek, Oct. 2001). This includes most mushroom anemones (corallimorpharians). However, as Charles Delbeek cautions, "One notable exception is the elephant ear mushroom anemone (Amplexidiscus fenestrafer). This animal is an active feeder on small fish and will envelope them whole with its mantle then slowly digest them by extruding its digestive filaments into the space created. No small fish are safe with these animals in the tank (Delbeek, Oct. 2001).".

Hippocampus also does very well with zooanthids and colonial polyps in general. But the hobbyist must be sure to observe a couple of precautions when handling the zoanthids and placing them in your aquarium.

First and foremost, many of the commonly available Zooanthus (button polyps) and Palythoa (sea mats) species contain a very toxic substance in their mucous coat known as palytoxin, which is one of the most poisonous marine toxins ever discovered (Fatherree, 2004). Palytoxin can affect the heart, muscles, and nerves, resulting in paralysis or possibly even death, and many hobbyists have reported numbness, nausea and/or hallucinations after merely touching these corals (Fatherree, 2004). When you handle zoanthids and palythoans, you cannot help picking up some of their protective slime on your fingers, and so much as rubbing your eye, picking your nose, or a small cut on your finger can be enough to land you in the hospital. When handling Zooanthus are Palythoa species, it’s very important to wear disposable latex gloves, avoid touching your mouth or eyes, and carefully dispose of the gloves immediately afterwards (Fatherree, 2004).

Secondly, zoanthids and other soft corals such as mushrooms may wage border battles if you place them in close proximity to each other (and the zoanthids almost always lose out to the mushrooms in these skirmishes). So be sure to allow adequate space between the colonies. Some rapidly growing Zooanthus colonies can be aggressive to soft and stony corals alike as they rapidly spread over the rockwork, but in general they are quite peaceful, and you can always slow down their rate of growth by reducing the nutrient loading in the aquarium.

Other low light corals that should be suitable for a seahorse reef include genera such as Cynarina, Scolymia and Trachyphyllia, as well as non-photosynthetic gorgonians such as Subergorgia and Didogorgia, and perhaps wire corals such as Cirripathes spp. (Delbeek, Nov. 2001).. However, supplemental feedings of zooplankton may be required to maintain these corals in good health.

The hard or stony corals fall into two categories depending on the size of their polyps. The small polyped stony (SPS) corals have tiny polyps that extend out of minute openings in the stony skeleton, and generally have weak stings that should not pose a threat to seahorses. Depending on conditions in the tank, SPS corals such as Acropora, Montipora, Pocillipora, Porities, Seriatopora and Stylophora can be tried freely at your discretion (Delbeek, Oct. 2001).

The large polyped stony (LPS) corals, however, are generally best avoided altogether. These include genera such as Catalaphyllia, Cynarina, Euphyllia and Trachyphyllia that have large fleshy polyps which often have tentacles equipped with powerful stinging cells. The Euphyllia and Catalaphyllia have the most powerful nematocysts among the LPS corals, and can deliver stings that are stronger than most anemones (Delbeek, Oct. 2001).

Some of the soft corals and stony corals that generally do well with seahorses in a modified reef tank are listed below. (By no means is this intended to be a comprehensive list, but rather just a few examples of suitable corals to serve as general guidelines when stocking a reef tank that will house seahorses):

Finger Leather Coral (Lobophyton sp.)
Flower Tree Coral – Red / Orange, (Scleronephthya spp.)
aka: Scleronephthya Strawberry Coral, or Pink or Orange Cauliflower Coral
Christmas Tree Coral (Sphaerella spp.)
aka: the Medusa Coral, Snake Locks Coral, or French Tickler
Cauliflower Colt Coral (Cladiella sp.)
aka: Colt Coral, Soft Finger Leather Coral, Seaman’s Hands or Blushing Coral.
Toadstool Mushroom Leather Coral (Sarcophyton sp.)
aka: Sarcophyton Coral, Mushroom, Leather, or Trough Corals.
Bullseye Mushroom Coral (Rhodactis inchoata)
aka: Tonga Blue Mushroom, Small Elephant Ear Mushroom (rarely)
Clove Polyps (Clavularia sp.)
Stick Polyp (Parazoanthus swiftii)
Green Daisy Polyps (Clavularia sp.), Indonesia
Orange & Green Colony Button Polyps (Zooanthus sp.), Fiji
Pulsing Corals (Xenia spp.)
Red Ricordea (Ricordea sp.), Indonesia, occasionally Solomon Islands
Lavender Hairy Mushroom (Actinodiscus sp.), Tonga
Pimpled Mushroom (Discosoma sp.), Indonesia
Purple Gorgonians

Best of luck with your ongoing research into the care and keeping of seahorses, lilypad!

Happy Trails!
Pete Giwojna