Ugh — I hate when that happens! I don’t know how many times over the years I’ve had seahorses ignore all my artfully arranged aquascaping and handpicked, thoughtfully placed finger sponges, colorful branching corals, lush beds of macroalgaes, and gorgeous gorgonia, only to adopt an unsightly siphon tube or the damned heater cord as their favorite hitching posts instead!
As you know, our amazing aquatic equines — especially the stallions — will often choose one particular hitching post as their home base and spend much of there time perched right there (think of your Dad hunkered down in his favorite easy chair in the den). Once they adopt a favorite base of operations like this, they will often proceed to change coloration to match their preferred resting spot. So I always take great pains to encourage my ponies to adopt one of the more vivid pieces as a favorite holdfast. Needless to say, it’s tremendously frustrating and annoying when they eschew all the primo hitching posts I’ve so carefully selected and arranged for them in favor of some piece of mechanical apparatus haphazardly dangling inside their tank! Doh!
You’re right, Tammy — that’s not a good place for your male to be hitching and hanging out, since it neutralizes the height advantage of your 30-inch tall aquarium and the protection and provides against gas bubble disease. Under certain circumstances, perching near the top of the aquarium can increase the risk that a seahorse will develop Gas Bubble Syndrome (GBS). To understand why this is so, you need to understand a little about the relationship between water depth (i.e., hydrostatic pressure) and the solubility of gases. Let me briefly explain:
The deeper you go and the greater the water pressure becomes, the more dissolved gases the water (and your seahorse’s blood) can hold in solution. By the same token, the shallower you go and the less water pressure there is, the less dissolved gases the water can hold and the more likely gas is to come out of solution and form gas emboli (i.e., seed bubbles) in your seahorse’s and tissues.
This means that there is a definite relationship between Gas Bubble Syndrome (GBS) in seahorses and aquarium depth. To put it in a nutshell, the shallower the water depth, the more likely GBS is to occur. There is considerable evidence that tanks 3 feet deep or more provide significant protection against GBS. This is because the gas emboli that cause GBS form more readily at reduced hydrostatic pressure, and will go back into solution again if the hydrostatic pressure is increased sufficiently, and obviously the deeper the aquarium the greater the hydrostatic pressure at the bottom of the tank.
Even if your aquarium is quite deep, however, your seahorses are at increased risk of GBS if they are always hanging out near the top of the aquarium. The lower hydrostatic pressure near the top of the tank allows gas emboli to form more readily, leaving the seahorses more susceptible to GBS than if they had remained at the bottom. To put it another way, if your aquarium is 4-feet tall but the seahorses are always hanging out in the top 1/4 of the tank, they might as well be living in an aquarium only 12 inches deep.
Does this mean that every seahorse that perches high up in aquarium will develop GBS? Not at all. If the aquarium does not experience gas supersaturation and is free of the other environmental factors that are conducive to GBS, the seahorses will remain free of gas embolisms no matter where they perch. But when the conditions in the aquarium are ripe for GBS (high CO2, low O2, low pH, gas supersaturation, stress, etc.), a seahorse that perches high up in the water column is much more likely to develop embolisms and fall ill than a seahorse that hangs out at the bottom of the aquarium.
For this reason, we want to encourage our seahorses to perch near the bottom of the aquarium where the hydrostatic pressure is greatest in order to take advantage while five of every inch of depth the aquarium can provide, and discourage them from habitually perching near the top where the hydrostatic pressure is lowest.
In many cases, there’s not too much the aquarist can do when& his seahorses tend to perch high up near the top of the aquarium. As often as not they seem to prefer heater cords, siphon tubes, filter intakes, powerheads and other aquarium paraphernalia as hitching posts over all the carefully selected macroalgaes, colorful corals, and sponges we painstakingly position in just the right place to attract their interest. The only sure way to prevent that sort of behavior is to choose an aquarium where all the equipment is self-contained behind a false back or is located in the sump for your seahorse setup.
In your case, Tammy, you’ll want to discourage him from perching on the powerheads near the top of your tank, if possible. Maybe you can reposition the powerheads to a location in the aquarium where your stallion can get at them. Or maybe you can remove them all together and use a spray bar return from a canister filter positioned just above the surface of the water to provide surface agitation and water movement.
All of your water quality parameters are excellent and the stallion isn’t having any problems thus far due to his tendency to perch on the powerheads at the top of your tank, but that’s a bad habit that you’ll want to eliminate for the sake of his long-term health.
Best of luck persuading your stubborn stallion to hang out near the bottom and take advantage of the other hitching posts you have provided, Tammy!