Waterflow for seahorses

Dear Dawn:

Good circulation is as important for a seahorse tank as any other aquarium. In general, you’ll want your filtration to turn over the entire volume of the aquarium at least 3-5 times per hour. So for a 20-gallon aquarium, try to assure that your filter moves a minimal of 60-100 gallons of water per hour.

As long as slack-water retreats are available, the greater seahorses can tolerate more current than most folks suspect. What they lack as swimmers is not agility, but rather stamina (Evans, 1998). They can hold their own against a brisk current, but not indefinitely, so low flow areas where they can move out of the current and hold when they want to rest are MUST be provided in addition to good circulation.

So does this mean the seahorse reef must be devoid of corals that do best in good water movement? No, just that the reefkeeper must be cognizant of the above and plan accordingly. 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 unpredictable surges and powerful water movement are 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, particularly if species with powerful nematocysts such as Euphyllia torch corals or Catalaphyllia elegant corals will be part of the exhibit (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 fairly 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, thereby creating eddies and slack-water zones where there is relatively little water movement downstream. 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 coarse sponge prefilter.

In short, if your filtration is not turning over the entire volume of the aquarium a MINIMUM of 3-5 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 achieve considerably higher turnover rates without producing too much turbulence or current for seahorses. 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. Remember, adequate surface agitation to promote efficient oxygenation and gas exchange at the air/water interface is just as important as the overall water movement.

But 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 a 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 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 downcurrent 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.

Best of luck adapting your 20-gallon reef tank for seahorses, Dawn!

Happy Trails!
Pete Giwojna