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A Beginners Guide to Seahorses

24 April 2009

The golden rule to keeping seahorses is to buy captive-bred stock. Thanks to retailers such as Simply Seahorses, this is not difficult to do. They regularly handle a number of different species, making it possible to choose precisely the right seahorse species for your aquarium and level of experience. Equally important is the fact that specialist seahorse dealers will know how to handle their livestock that bit better than the average retailer. You can expect their stock to be well fed and in prime condition.

For a variety of reasons, wild-caught seahorses rarely do so well in captivity. The biggest problem is feeding them; wild-caught seahorses almost always prefer live foods and unless given a sufficiently varied diet, gradually starve to death. Another problem with wild-caught seahorses is disease. The stress of capture coupled with a certain level of malnutrition seems to predispose wild-caught seahorses to a variety of diseases, particularly bacterial infections caused by Vibrio and Mycobacteria spp. Even when treated with antibiotics, many seahorses so infected fail to recover.

The bottom line is that aquarists are better off ignoring wild-caught seahorses, however temptingly they are priced. Except in the hands of very expert fishkeepers, such specimens can't be expected to live for anything like their normal lifespan of 3-5 years. By contrast captive-bred seahorses are a good investment. They settle into aquarium life well because they've never encountered anything different, and both breeders and specialist retailers take care to minimise problems with malnutrition and disease. Because seahorses are relatively easy to breed, by marine fish standards at least, a reasonably skilled aquarist can even establish a colony of these intriguing fish without too much difficulty.

General requirements

Most seahorses are strictly saltwater fish in the while, though some can be found brackish water habitats as well. The species most commonly traded are marine fish, so they will need to be kept in a marine aquarium. This means that the aquarist will need to establish a fully-cycled marine aquarium system before buying any seahorses.

Experienced aquarists will not find this particular aspect of seahorse maintenance especially challenging; seahorses are, by the standards of marine fish at least, fairly hardy and adaptable. For example, the precise salinity doesn't matter all that much, provided it is stable, and anything between SG 1.020 and 1.025 will suit most species. In terms of aquarium size, something upwards of 75 litres will suit a wide variety of seahorse species in either the groups or matched pairs within which they are best maintained. Filtration should be efficient rather than vigorous, and a water turnover 4-6 times the volume of the tank will do for most species. Undergravel filtration can be used, though a system equipped with live rock and an external canister filter for mechanical filtration is perhaps the ideal. Protein skimmers are useful rather than essential tools, and will certainly make water quality maintenance a good deal easier.

On the other hand, aquarists coming over from the freshwater side of the hobby will need to review the basics of marine fishkeeping before taking the plunge. Such aquarists should take the time to read one of the many excellent books available to newbie marine aquarists, such as Bob Fenner's excellent Conscientious Aquarist.

Temperature

Seahorses come from tropical, subtropical and temperate zone environments, and the temperature of the aquarium will need to reflect the needs of the species being kept. By standards of coral reef fish though, even the tropical seahorse species prefer slightly cool conditions, the ideal being around 23-25 degrees C. Subtropical species will need to be kept at around 18-20 degrees C, while temperate zone species are happier at around 15-16 degrees C.

Keeping tropical and subtropical seahorses at the right temperature is generally no more difficult than setting the heater thermostat to the desired setting. But temperate zone species can become stressed by summer temperatures, even in England. Putting the tank in a cool room or basement is ideal, but otherwise you may need to find some way to cool the water.

One useful method is to fill plastic ice cream tubs with water and then freeze them solid. When required, you can float the tubs in the aquarium, and as the ice inside melts, they'll cause the aquarium to cool down. It's a good idea to have two or more such tubs, so you can cycle them through hot spells, with one cooling down the tank while the others are being frozen.

The other popular method is to use a chiller. These can be purchased from aquarium shops. They are expensive, but will lower the temperature safely and effectively. Do remember that it the chiller cools the tank down by more than a few degrees condensation will form on the outside of the tank. Precisely when this happens will depend on ambient air temperature and humidity.

Social behaviour

The majority of adult seahorses form pairs in the wild, some ichthyologists believing that the two fish are faithful to one another for their entire lives. Some species live in groups though, and you will need to establish if this is the case when selecting seahorses. Social species should be kept in groups of six or more specimens, while pair-forming ones should be kept in male/female pairs.

Pair-forming seahorses can be territorial, and unless that tank is reasonably large, they are best kept in a tank of their own. The smaller species around 10-15 cm length will require upwards of 75 litres per pair, while larger species will need proportionally more.

Tankmates

By default, seahorses are best kept alone; they certainly don't need companions. One key problem is that seahorses are slow feeders, so any tankmates will need to be equally slow, otherwise the seahorses will lose out. Things like clownfish and damselfish might seem viable, but really aren't. If you must keep your seahorses with tankmates, look for things like gobies, dragonets and blennies that feed just as slowly as seahorses.

Invertebrate companions can be tricky, with boxer shrimps, crabs, green brittlestars and most anemones being well able to catch and eat seahorses, given the chance. Inexperienced hobbyists will probably find sticking with live rock and a few carefully selected polyps and leather corals the best approach. Turbo snails and other small algae-eating snails would also work well. Featherduster worms and giant clams can be kept with seahorses, but they are very difficult to maintain, and are best left to the more experienced hobbyists.

Diet

Most but not all of the species bred in captivity will take frozen foods without complaint. These include popular species such as the tropical species Hippocampus kuda and the temperate species Hippocampus erectus. The most notable exception is the subtropical pygmy seahorse Hippocampus zosterae, a species that appears to be too small to accept frozen foods and must be fed newly-hatched brine shrimp on a regular basis. As such, this is one species best avoided by inexperienced hobbyists.

In general, the seahorses that accept frozen foods are normally reared on frozen mysis shrimps. Ideally, these should be fortified or otherwise nutritionally complete mysis shrimps, but failing that, the use of a marine fish vitamin supplement is recommended. Seahorses will also take whatever copepods and other small animals they find in the aquarium. In the past it was quite common to feed large seahorse species livebearer fry, particularly black molly fry, but there's no advantage to doing this and it is not recommended.

Tropical species

The tropical species will need to be kept at 22-25 degrees C to do well, which is slightly cooler than the average tropical marine community or reef tank. Among the tropical species traded are Hippocampus angustus, Hippocampus barbouri, Hippocampus comes, Hippocampus erectus, Hippocampus histrix, Hippocampus kuda, and Hippocampus reidi.

Hippocampus erectus is a good species for the beginner. Although primarily a resident of the Gulf of Mexico in the tropical Western Atlantic, it has an astonishingly wide range in the wild, being found as far north as Nova Scotia! It is also quite a big fish, with an average length of around 15 cm but exceptional specimens can be as long as 20 cm. It is a robust and hardy species, and provided it is well fed, it is a reliable aquarium resident. Hippocampus erectus are normally found in pairs and can be territorial in captivity.

Hippocampus reidi is another large species, in some cases specimens reaching lengths of 30 cm! Though the average specimen is quite a bit smaller, obviously these fairly big fish will require a sizeable aquarium. This is a territorial, pair-forming species. It is native to the Gulf of Mexico and Caribbean area, but is noted for coming in a variety of different colour forms, perhaps related to the local environment.

Subtropical species

Subtropical species are best maintained substantially below normal tropical temperatures; 18-20 degrees C is recommended. There are several species traded, including Hippocampus breviceps, Hippocampus coronatus, Hippocampus subelongatus, and Hippocampus zosterae.

Hippocampus breviceps is a relatively small (10 cm) species from Australia. It is one of the gregarious species best kept in groups, though it may be maintained as a pair instead. Wild fish are found in relatively deep, cool habitats and it becomes stressed if the temperature gets too high.

Hippocampus zosterae is one of the smallest seahorses at under 5 cm in length, and noted for its ability to change colour depending on its mood and environment. Wild fish live in seagrass meadows along the Atlantic coastline of the Southern United States. They are gregarious and best kept in groups of six or more specimens. Although routinely bred in captivity, this species is too small to take frozen foods, and can only be maintained on live foods, particularly brine shrimp nauplii. While a fascinating species in many ways, it is only suitable for very advanced aquarists.

Coldwater species

It is a surprise to many Britons that there are two seahorse species native to these islands: Hippocampus hippocampus and Hippocampus guttulatus. Both are found in shallow water habitats particularly along the South Coast, with seagrass meadows being particularly favoured. As you'd expect, temperate zone seahorses need quite cool water conditions to do well, and while an aquarium in an unheated room may be adequate most of the time, in some cases a chiller will be required. A temperature of 15-18 degrees C is recommended for the temperate zone seahorse species regular traded such as Hippocampus abdominalis, Hippocampus capensis, and Hippocampus guttulatus.

Hippocampus abdominalis is known in the trade as the "pot-bellied seahorse" because of its distinctly portly build. It is a very large species, with specimens more than 30 cm in length being known. Besides being gregarious, this species is also very active, and groups will spend much more time swimming about in midwater than most other seahorses. Obviously these fish will require a very big aquarium to look their best, certainly upwards of 250 litres. Apart from the need for space and cool water, they are not especially difficult to keep, and make fantastic fish for the reasonably advanced aquarist looking for something a bit different.

If you would like to learn more about Simplyseahorse and view their full stock list click here.