Re:current question

Dear Sandy:

You’re very welcome! It’s encouraging that your new seahorses took to the baster feeding so quickly, and it sounds like your pipefish is doing a great job of cleaning up the leftovers. That will be very helpful in maintaining good water quality with these messy eaters.

With regard to the current in your Nano tank, Sandy, time and time again I find that home hobby tanks have far too little water movement. In my experience, most seahorse setups are chronically undercirculated, a serious mistake for small, closed-systems aquaria, and our pampered pets often suffer as a result. Many hobbyists are overly conscious of the seahorse’s inactive life style and limited swimming ability, and have adjusted their flow rates accordingly, resulting in less water movement than desirable. 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! Avoid dead spots and stagnant areas at all costs.

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. 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."

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. I cannot emphasize that enough. What they 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.

One good way to accommodate both the need for good water flow and circulation and the seahorse’s need for slack-water retreats is to create tall rock formations a foot or two down current from the strongest outflow 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.

In addition to an external power filter, my SHOWLR system 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.

In short, if your filtration is not turning over the entire volume of the aquarium a MINIMUM of 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 turnover rates of up to 10-20 times the volume of your tank every hour 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.

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 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 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 with your new seahorse setup, Sandy! If you can convert the output from your filter to a spray bar return with the help from the guys at your LFS, that should correct the situation and minimize any problems you may be having with excessive currents.

Respectfully,
Pete Giwojna