Re:walking the temperature line

Pete Giwojna

Dear eaglestour:

Yes, sir, you are quite corrfect — heat stress can indeed be very debilitating for seahorses and must be avoided. The highly domesticated Hippocampus erectus is surely the hardiest of all the cultured seahorses and can adapt successfully to a wide range of temperatures, but Mustangs and Sunbursts (H. erectus) are raised at 73-75°F at the Ocean Rider aquaculture facility and that is the optimal temp for them. They don’t tolerate temperature spikes above 80°F well, so your summertime Carolina heat waves would also be problematic for H. erectus.

There are a few simple measures you can use to cool down the aquarium and counteract the overheating problem: For example, a simple way to drop the water temp in your aquarium is to position a small fan so it blows across the surface of the water continually (Giwojna, Oct. 2003). This will lower the water temperature a several degrees via evaporative cooling (just be sure to top off the tank regularly to replace the water lost to evaporation). Leaving the cover/hood and light off on your seahorse tank in conjunction with evaporative cooling can make a surprising difference.

In a pinch, some hobbyists will even freeze plastic bottles 3/4 full of water and float the frozen bottles of water in their tank during the hottest part of the day. If necessary, that may worth trying in your case too, depending on how well your aquarium temp responds to the other measures.

Here are some additional suggestions on cooling down your aquarium from Renée at the org that you may also find helpful:

Some summer tips are:

· Use computer fans (you can wire them to AC adapters… we are making some this weekend for our tanks).

· Use a big ol clip-on-fan or a fan on a stand that you can set close. (Just be mindful of water evap.)

· Float ice containers in the tank (Use water/liquid that you wouldn’t care if it sprung a leak. Those blue lunch/picnic type cooling things are not acceptable IMO…. what if it leaks? It will kill everything. I would recommend using bottled ice water because it will stay frozen even longer than fresh water….. but if you do use fresh water make sure it is water you wouldn’t mind spilling into the tank…. good ole tap water is not acceptable.)

· If you have a hood or canopy on the tank…..keep it off or lifted.

· Cool down the room the tank is in by using a portable or window AC unit. The window units can be pretty cheap.

· If the sun really heats up this room, look into some window tinting. This is what I did when I lived in South Texas. It dropped the room temp TEREMENDOUSLY! (If ya wanna go the cheap method, foil was used in many windows in the city I lived in… wasn’t the prettiest method but it saved many people lives who lived in places without central AC and couldn’t afford well working window units.)

· Shorten your photoperiod…. if possible don’t have the lights on in the hottest past of the day. But at any rate, shorten the amount of hours the lights are on for.


Since warm-water holds less dissolved oxygen than cooler water, in addition to cooling down the aquarium gradually, it’s also a good idea to increase the aeration and surface agitation is much as possible in order to improve oxygenation and promote efficient gas exchange at the air/water interface. That will raise those dissolved oxygen levels even quicker than cooling the aquarium will, so consider adding an ordinary airstone or two, at least until the aquarium temperature has gradually dropped down closer to the 73°F-75°F range again.

Aside from your basic water quality tests (ammonia, nitrite, nitrate, and pH), I also recommend that you use a test kit for measuring the dissolved oxygen in your seahorse setup from now on. The reason for this is that a drop in the level of dissolved oxygen is a great early warning indicator that something is amiss in the aquarium, and can thus predict potential problems (and allow you to take corrective measures) BEFORE they become full-fledged disasters. For example, a drop in O2 levels could be an early indicator of overcrowding — a signal that your system has reached its carrying capacity. Or it may merely signal a rise in the water temperature due to a summertime heat wave or indicate that the tank is overdue for a water change and/or a thorough cleaning to remove excess organics and accumulated detritus. Or it could be telling you that your tank is under circulated and you need to increase the surface agitation and water movement.

The point is that checking the O2 levels in your aquarium can alert you to impending problems and allow you to do something about them before they have dire consequences. A drop in O2 levels is often the first sign of a water quality problem and it can tip off the alert aquarist that trouble is brewing before his seahorses are gasping for air in obvious respiratory distress. Checking the dissolved oxygen levels regularly is the next best thing to continuously monitoring the Oxidation-Reduction Potential (ORP) or redox of the water, which is a luxury few hobbyists can afford.

The Tetra Oxygen Test Kit (TetraTest 02) is an adequate liquid reagent test kit for fresh or saltwater with simple color scales for comparing readings that tests for 02 in the range of 2-14 ppm (the optimum dissolved O2 level is 6-7 ppm). It will cost you between $8.50 to $14 depending on where you shop and should be available at any well-stocked LFS. Salifert also makes a nice 02 Test Kit (their 02 Profi-Test) that will run you about $20.

There are some very affordable mini aquarium chillers that could easily be mounted on your 35-gallon tax tank, but they are designed for smaller aquaria and wouldn’t make much of a dent in the water temperature on an aquarium of that size. For example, the CoolWorks Ice Probe and Microchiller units are ideal for small tanks (10-15 gallons) will drop the water temperature up to 6-8°F below the ambient room temperature:

Click here: CoolWorks Ice Probe with Power Supply – Marine Depot – Marine and Reef Aquarium Super Store

Click here: CoolWorks Microchiller – Marine Depot – Marine and Reef Aquarium Super Store

Your hex tank would need a larger chiller than either of those units, however, at which point you’re going to be talking about a chiller that costs several hundred dollars, so I’m not sure if you wanna go that route. I’m not certain how well larger chillers would fit on the hex tank design either.

Another approach would be to select tropical seahorses that can handle temperatures around 80°F and be comfortable in a system like yours. Several of the reef dwelling species are good candidates for a tank like yours. For example, H. ingens, H. barbouri, H. comes, H. kuda and to a lesser extent H. reidi are all warm-water seahorses that prefers somewhat warmer temperatures. These species can all adapt to temperatures up to the 78°F-82°F (25°C-28°C) range. So if you can employ some of the simple measures we discussed for lowering your water temperature a few degrees, and then stock your tank with H. barbouri, H. ingens, etc. that can better tolerate occasional summertime temperature spikes into the lower 80s, that might be an option that will work well for you.

The Gigante or Pacific seahorse (H. ingens) is accustomed to equatorial heat and is an excellent choice for warmer tanks like yours. Hippocampus ingens are true giants among the seahorses. They can reach a length of 36 cm or more than 14 inches when fully grown, making them the world’s largest seahorses, rivaled only by the biggest examples of H. abdominalis (Giwojna, June 2002). The prehensile tail of a large adult has a powerful grip like an anaconda, and they can exert enough pressure to leave you counting your fingers afterwards when they squeeze down.

But despite their great size and power, these gentle giants are not at all the brutes you might imagine. They are close relatives of the Brazilian seahorse (H. reidi), and share its slender profile and graceful proportions (Abbott 2003). Imagine a seahorse with the same sleek silhouette as reidi, but which reaches twice their size, and you will have a pretty good picture of what H. ingens is like (Abbott 2003). They are stately steeds, built like thoroughbred racehorses, which carry their size very well. The crowning touch for the King of all the seahorses is a tall, backward-swept, five-pointed coronet, which adds to their majestic appearance (Abbott 2003). The Hawaiian strain of captive-bred ingens is a bright golden yellow, often further adorned with a lacy latticework of vivid purple-to-lavender lines.

The Spikey or prickly seahorse (Hippocampus barbouri) also prefers warmer temperatures than most other seahorses. All seahorse keepers are familiar with these thorny beauties. They are the pretty, prickly, tropical seahorses we all used to know and love as Hippocampus histrix until the histrix complex was revised and taxonomists officially changed their name to H. barbouri (Abbott, 2003). They are readily identified by their sharp, very well developed spines, their prominent five-pointed crown, and their boldly striped snouts (Abbott, 2003). The latter is one of their most attractive features and is responsible for one of their common names — the zebra-snout seahorse. Cultured specimens range from pale yellow to a brilliant red-orange, often further adorned with reddish brown spots and lines.

Tigertail seahorses (Hippocampus comes) are among the most beautiful and boldly marked of all seahorses. Their beauty is not due to vivid colors but rather to their striking pattern and graceful proportions. They are sleek, slender seahorses built like greyhounds. With their long snouts and slim profiles, these smooth-bodied seahorses seem almost streamlined. Their elegant proportions and bold stripes make Tigertails highly prized by all seahorse keepers.

As you might expect from their common name, a beautifully striped tail is the trademark of Hippocampus comes. Many Tigertails also display an attractive mottled or blotched pattern on the body with a network of fine white lines radiating from the eye (Giwojna, unpublished text). In the best specimens, the contrasting bands on the tail extend well up onto the body in the form of alternating light and dark blotches. Well-marked yellow-and-black H. comes are particularly striking — when the yellow is bright, they look especially tigerish!

The ever-popular Brazilian seahorses or Brazileros (Hippocampus reidi) are sleek, graceful animals, perfectly proportioned with slender bodies, long tails, and long snouts (Abbott 2003). Their lithe appearance gives rise to their other common names, the Slender Seahorse or the Longsnout Seahorse (Abbott 2003). Whereas the robust H. erectus is a solidly built seahorse like a Mac truck, H. reidi shares the graceful curves of a Corvette Stingray (Abbott 2003). The result is an elegant warm-water seahorse that is everyone’s all-time favorite:

Long renowned for their brilliant colors, rapid color changes, prolific breeding habits, and huge broods of difficult-to-raise fry, all serious seahorse keepers are familiar with these breathtaking beauties (Giwojna, Jun. 2002). Often proclaimed the most attractive of seahorses, H. reidi is the crown jewel in many aquarists’ collections. These rather majestic steeds are long-lived, and with good care, they will be your companions for the next 8 to 10 years and may eventually reach a length of 7 inches (Abbott 2003; Giwojna, Jun. 2002).

This species regularly produces some of the most brilliant color morphs I have ever seen. Going from most to least common, these sports include bright yellow, orange, and red individuals, which are much sought after by aquarists. The yellow, orange, and red morphs of H. reidi have all been established by aquaculturists and are now readily available.

Best of luck with your new seahorse setup, eaglestour!

Happy Trails!
Pete Giwojna

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