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Photo: Prilfish

Keeping seahorses in an aquarium – possible, but difficult


Photo byPrilfish

It’s hard to deny the appeal of keeping seahorses at home but there’s dedication and planning required if you’re going to make these creatures feel at home in your living room. Are they as hard to keep as you’d imagine? 

An introduction to seahorses

All in all, there are 54 members of the genus Hippocampus and they are much more widespread than you may have previously believed. From the Pacific Ocean to the Mediterranean sea, they can be found in the shelter of mangroves, seaweed and coral reefs. The Short-Snouted Seahorse, Hippocampus hippocampus, more accustomed to the Canary Islands than cold UK waters, has even been found in the Thames estuary.

There aren’t any prizes for guessing how the seahorse got it’s name however they aren’t so horse-like in their size: They range from the tiny Pigmy Seahorse, H. bargibanti, which will barely exceed 2cm to the Pot-Bellied Seahorse, H. abdominalis, which reaches 35cm in length.

Indeed the seahorse is an unusual fish, not least of all because it swims upright, the only other fish sharing this behaviour being the Razorfish, but also because they are remarkably poor swimmers. In fact, the slowest moving fish is the Dwarf Seahorse, H. zosterae capable of a very leisurely 1.5 meters per hour. They swim by rapidly vibrating their dorsal fins and steering with their pectoral fins. In most cases you will find them wrapping their tail around an object whilst they use their snout to catch prey – something they do at great speed. Their bodies aren’t like that of most other fish either, made up of an external skeleton consisting of bony rings covered with skin.


Photo: Stephen Childs

Keeping seahorses in the aquarium

It is possible to keep seahorses in an aquarium and they are actually one of the relatively few marine fish species that can be captive bred. Evidently there are very few aquarium stores willing to stock seahorses but it is sometimes possible to make a request or contact a specialist seller. Expect to pay a large sum for most seahorses.

In any case, you must be experienced and knowledgeable to the point of your friends considering you a bore before you can attempt to take on these demanding creatures.

The tank

Ideally this should be as tall as possible as seahorses are vertical swimmers with at least 10 gallons of water per seahorse. Larger species will need larger tanks and finding an aquarium tall enough may be a problem. Tall square-based or hexagonal tanks would be ideal, as would a corner aquarium as these all tend to be taller than a rectangular equivalent.

Heating and lighting

Seahorses prefer slightly cooler temperatures than most marine fish at 23-24°C, however this can vary by species. This means you are even more likely to need a cooler device for the summer months in which temperatures can top 30°C even in the UK. Lighting shouldn’t be too bright and the standard light that comes with your tank should suffice. This will have repercussions if you wish to keep corals with your seahorse but never try adding extra lighting to satisfy the needs of the latter to the detriment of your seahorses.


First and foremost, seahorses need something to hold on to with their tail. It’s better if that something is vertical. Natural suggestions would be seagrass, kelp or macroalgae such as Caulerpa. If, as will be the case for most people, these things are hard to come by, artificial substitutes can be used; I have even seen a sunken rope in a public aquarium which made for an excellent seahorse display.


Now here we come to the really tricky part. Not only are seahorses exceptionally intolerant of unhealthy water and are likely to protest against the slightest trace of ammonia by dying, but they are also unable to cope with constant strong currents. This all but rules out the possibility of blasting water around a tank full of live rock. A small powerhead would be acceptable for most seahorses and positioned in such a way that it agitates the surface would be best unless your are trying to breed your seahorses.

A cannister or hang on filter could be an option, as could a sump but you must ensure no strong currents are produced by returning water. A sump would be good as it increases the volume of water in your aquarium and its larger size and filter media capacity would allow for a slower turnover rate. Water flow must be well distributed so that the turnover rate is high enough to keep the water very well filtered, but without causing strong currents.

If that didn’t seem difficult enough, a seahorse doesn’t have particularly effective gills or digestive system. The problem that this creates is that they are constantly eating and partially digesting a greater volume of food than other fish need to eat. This means you need to remove a fair amount of decaying material and the resulting ammonia production, but also keep the water well aerated. The best solution, and an indispensable piece of equipment when keeping seahorses is the protein skimmer which both oxygenates the water whilst removing organic waste.


Instead of telling you myself, here’s an absolutely fantastic web page from seahorse.org on seahorse tankmates.


Photo: Prilfish


The difficulty with feeding seahorses is that they not only have short, inefficient digestive tracks but that they are also very fussy with what they eat. Even live food isn’t a guaranteed success.

When it comes to feeding it is much easier if you have a captive bred seahorse as it will be much more willing to accept frozen food. Otherwise, you’ll have to either accustom your seahorses to eating frozen foods, particularly mysis shrimp or provide them with live food. This can be difficult and will require a lot of prior planning to ensure you have a ready supply of live food. Brine shrimp should not form the basis of your feeding routine either. Brine shrimp should only be fed to seahorses if they are newly hatched and even then, many seahorses will ignore them.

Ghost Shrimp and Mysis probably represent your best bet at finding and culturing a food supply for your seahorse. They are easy to find and reproduce very quickly. Other food sources include Isopods and Amphipods which are often found in marine aquariums without having been intentionally introduced. Some people even keep some livebearer fry on standby in case they run out of food. Enrichment and gut loading are common practices carried out to ensure good nutritional content in live foods.

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