Secrets For Success: Rules You Should Follow To Keep Your Seahorse Aquarium Thriving

So you’re interested in seahorses? It’s easy to see why!

Seahorses are some of the most interesting and unique fish on the planet. They make great pets and can become quite tame. They know who their humans are and will interact with you in ways other fish can not. They can learn to eat from your hand or even hitch on your fingers. You may find that your favorite pet seahorse greets you each morning with a special dance.

Keeping seahorses is not more difficult than keeping a reef aquarium, it’s just different. If you have reefkeeping experience, you will need to unlearn some of what you know and follow a set of seahorse-specific rules.

Rule #1: Buy Captive Bred Only

Do not buy wild caught or net pen-raised seahorses. Wild caught and net pen-raised (maricultured) seahorses are initially less expensive than captive-bred seahorses, but end up being more expensive in the long run. They most often carry pathogens that are expensive to treat and don’t always respond to the over-the-counter medications available to hobbyists.

Seahorse breeders sometimes purchase wild caught and net pen-raised seahorses if the species isn’t available as captive-bred. Experts recommend wild caught and net pen seahorses are always treated with a number of medications in a quarantine tank for a minimum of 9 weeks, but their survival rate is still fairly low. They usually won’t eat frozen foods and are already “walking dead” from starvation and handling stress when they arrive at your local fish store. Even if a seahorse is eating frozen food, if it is wild-caught or net pen raised, chances are good that it’s carrying pathogens that will make it a ticking time bomb.

Only buy captive-bred seahorses raised by a breeder who uses a salt mix or properly sterilized seawater. There are a few reputable breeders here in the United States and Europe. You can order directly from the internet or ask your LFS to order them for you.

Ask other seahorse keepers in online forums or Facebook groups which breeders they recommend. You can sometimes find captive-bred seahorses at your local fish store. Ask the owner or fish buyer who bred the seahorses. If they don’t know, pass. If the breeder isn’t listed on their invoice, it’s probably net pen raised or wild-caught. If they know who the breeder is, they’ll want to advertise that because captive-bred seahorses are hardier and more valuable. Some net pen-raised seahorses are sold as “tank raised” or “tank bred,” but the breeder isn’t known. In those cases, they’ve likely been raised in the same conditions as net pen-raised seahorses and carry the same risks. Always find out who bred the seahorse before purchasing to ensure quality.

An exotic, spiky H. barbouri from SeahorseSource, a breeder in Florida

Captive-bred seahorses, especially the US endemic Hippocampus erectus, are quite hardy. Contrary to popular belief, seahorses are not particularly fragile when they’re in good condition. They’re much more tolerant of handling than other fish because of their physical build. These demersal animals spend most of their lives with their tails and bodies wrapped around objects in their environments.

Just like puppies, seahorses should be a certain size and age before going to their new homes. It varies by species, but the common H. erectus should be 4 - 6 months old and at least 3” long before you add it to your aquarium. Seahorses smaller than this may not transition well to a new environment and require 4 or more feedings a day. Mature seahorses are hardier and only need 2 or 3 feedings a day. Most reputable breeders won’t sell their seahorses while they are small and still require many feedings a day.

If you’re buying seahorses from your local fish store or a local breeder, choose active seahorses with full bellies. Sunken sides are a clear indication of starvation and malnutrition or internal parasites. Ask to see the seahorses eat. They should be able to aim for the food accurately and not miss or struggle to suck food into the snout. Look for clear eyes and skin without lesions or swollen areas. It’s normal for seahorses to have a covering of fuzzy algae or Cyanobacteria growing on them.

Young seahorse fry covered in algae

Rule #2: Keep Your Tank Clean

Seahorses are not designed to eat dead food; in the wild, they only eat live prey. Seahorses lack the gut-associated lymphoid tissue in their digestive tract that helps protect most other fish from bacteria on decaying food. This is why it is very important to only offer very fresh frozen foods. If your frozen mysis is more than a few months old or looks brown instead of white, throw it out. Bacteria like Vibrio and Mycobacterium will quickly colonize decaying organic matter in the aquarium, and seahorses are particularly susceptible to these bacteria. If there is leftover food on the bottom of the tank, make sure to quickly siphon it out within an hour after feeding. It’s also wise to siphon out any feces before feeding to prevent accidental ingestion. You can use a simple hose and bucket or a siphon hose that hooks up to the sink. Use an algae scraper like a Mag-Float to clean walls regularly. When you change your filter media, make sure you scrub inside your tubing, pumps, and filters as well.

Yellow H. erectus on a red sea star.

Rule #3: Maintain the Right Temperature

Seahorses do best in temperatures a bit lower than reef aquariums. Hippocampus erectus prefer temperatures between 68° F and 74° F. Other tropical species like H. reidi, H. comes, and H. kuda like slightly warmer temperatures between 72° F and 74° F. It is true that wild seahorses can be found at higher temperatures in the wild, but since tropical Vibrio bacteria thrive and become more virulent at temperatures above 74° F, captive seahorses do best at or below 74° F. If you’re keeping sub-tropical or temperate seahorses, ask the breeder or a seahorse expert what the correct temperature is for that species.

If you can not maintain a temperature of 74° F or below in your seahorse aquarium, you can use a fan to blow across the top of the water to bring the temperature down a few degrees. The water will evaporate quickly, so have plenty of fresh water on hand to top off the tank. If you need to bring the temperature down more than a few degrees, an aquarium chiller is recommended. You should choose a chiller that is slightly oversized, as this can increase its efficiency and lifespan. If your air conditioner breaks or your power goes out on a hot summer day, have plenty of frozen water bottles in your freezer that you can float in your seahorse aquarium to help keep the temperature cool.

Some seahorse aquariums won’t need a heater. If your home temperature in the winter is too cool or your home’s temperature is unstable, you will need a heater. Never put a regular aquarium heater in the main display where seahorses have access to it. Unlike other fish that swim, seahorses will hitch on the heater. When the heater turns on, it will burn the seahorse which can lead to severe injury, infection, and death. You can keep your heater in a sump filter or the back filtration chamber of your all-in-one Innovative Marine or Red Sea tank, or use an in-line heater so your seahorses can not hitch to it.

H. erectus fry about to eat a live adult brine shrimp

Rule #4: Always Quarantine and Condition

It is strongly recommended to quarantine new seahorses, even if they are captive-bred and you trust the breeder and supplier wholeheartedly. Seahorses are most often bred in large, sterile vats with one type of hitch and no sand or rock. When you bring home a new seahorse, chances are they’ve never experienced a typical aquarium environment, and it can take some time for them to get used to it. It’s not uncommon for even captive-bred seahorses to stop eating frozen food when they’ve gone through shipping stress and then moved to a new environment. This is why quarantining them in a system that is similar to what they were raised in can increase your chances of keeping them alive. Seahorses are much more likely to eat frozen food in a bare-bottom tank than in a tank with sand. Condition and observe your new seahorses in the quarantine tank for at least 30 days before moving them to the display. Even if they’re your first seahorses, it’s a good idea to quarantine them so they can gain their strength before moving to the display. This will also allow you to observe them for any possible health issues or pathogens that you don’t want to infect the display tank with.

A simple, dimly lit bare bottom tank with a few hitches and a few pieces of cured live rock make a good quarantine tank. You can use cycled sponge filters or HOB filters. Feed at least twice daily and siphon uneaten food within an hour after feeding. Test the ammonia and pH daily and do water changes as needed.

If you have chosen to purchase wild-caught or net pen-raised seahorses, quarantine and conditioning are a necessity. The process is much longer, more complex, and involves a minimum 9 weeks of de-worming treatment and frozen food training.

Australian pot-bellied seahorses require very chilly water to thrive.

Rule #5: Give Them Room to Grow

Most people only ever see young seahorses in person at pet shops. H. erectus and H. reidi can reach over 7” in length, some growing larger than an adult’s hand. You may be tempted to buy a smaller tank for young seahorses, but they grow so quickly you’ll need to upgrade to a larger tank within a few months.

erectus and H. reidi need a minimum of 30 gallons per pair, but do better with a 50 gallon or larger. Add 20 gallons for each additional pair. If you overcrowd your tank, you’ll find yourself struggling to maintain the water quality and prevent illness in your seahorses. This will end up costing more money and causing you and your seahorses undue stress.

Appropriately sized all-in-one tanks with open tops are perfect for seahorses. Enclosed all-in-one tanks like the Biocube and Nano Cube tend to run too hot for keeping seahorses. Innovative Marine, Red Sea Max, and Red Sea Reefer style tanks are great options for seahorses. Seahorses prefer at least 24” of vertical height for their elaborate courtship and mating rituals.

It can be tempting for a lot of reefers to put seahorses in their existing aquarium’s sump away from their stinging corals and aggressive fish, but this is not a good idea. Reef temperatures tend to be too high for seahorses, and sumps, just like any filter, collect detritus that can attract bacteria and make your seahorses sick if they come in contact with it. Your skimmer pumps and return pump are a major risk for seahorses inside a sump; if they go through a divider or baffle, their tails can easily be caught and destroyed in these pumps.  Seahorses are messy eaters and will increase the nitrate and phosphate levels in your reef tank. Seahorses and other fish belong in the aquarium, not inside a filter.

If you would like to keep seahorses in an aquarium plumbed into your existing aquarium, keep in mind that the temperature will need to be lowered for the health of the seahorses. You will need to do more frequent water changes to control the nitrates and phosphates resulting from your seahorses’ feeding behavior. Hardy corals may do well in an aquarium shared with seahorses, but corals like SPS that prefer very low nitrates and phosphates and warmer temperatures may not thrive.

Rule # 6: Proper Filtration and Flow Are Key

It is imperative to have enough flow and filtration in your seahorse aquarium. The advice to keep seahorses in a low-flow aquarium is outdated. Years ago the majority of seahorses available were small, weak specimens that couldn’t handle normal flow, and this misconception that seahorses need low flow has persisted. The hardy, robust captive-bred specimens available today thrive aquariums with normal flow rates. It’s perfectly acceptable to have ten or even 20 or more times turnover in your seahorse aquarium. What isn’t acceptable is a direct jet of flow or if the seahorses have nowhere to swim, dance, or escape heavy, turbulent flow. A spray bar or circle flow assembly can help you eliminate dead spots in the aquarium while giving your aquarium a gentle but high flow rate.

A beautiful pipefish and seahorse reef at the Shedd Aquarium with high flow

Avoid using powerheads or wavemakers in a seahorse aquarium. Seahorses will hitch to the powerhead grate and can get their tails stuck or severely injured by the impeller. If you have a powerhead, you must use a cover or net like a media bag that fits over the entire powerhead because a seahorse can even get into the front of a powerhead with strong flow. Covers on powerheads can be unsightly and will restrict the flow, but frequent cleanings can help.

The best type of filtration for a seahorse aquarium is a sump (the Red Sea Reefer all-in-ones come with simple to install sump filters). A sump can increase total system volume and has room for protein skimmers, refugium, and media reactors. If your tank is not “reef ready” or drilled, you can add a hang on the back over flow box along with an aqualifter pump. Choose a sump and an properly sized return pump.

If you decide not to use a sump, choose the largest canister filter or HOB filter you can find. Seahorses require heavy filtration, so you’ll regret buying a filter that is merely adequate. With frequent feedings and waste, Seahorse tanks must have effective mechanical filtration—such as filter socks, sponges or filter floss—to remove particulates from your aquarium water. These mechanical filters need to be cleaned or replaced often to avoid a build-up of nitrates.

A skimmer is a highly recommended piece of equipment for a seahorse tank. It was once believed that rogue skimmer bubbles were responsible for Gas bubble disease and pouch emphysema, but today we know that isn’t true. Skimmers actually prevent these ailments by driving off supersaturated gases and removing organics. (prevent GBD by keeping nitrates and organics low and always match the temperature of your water change water.)

UV sterilizers are another must-have piece of equipment. They won’t entirely eliminate pathogens like Vibrio, Mycobacteria, Uronema, and ciliates, but along with proper tank maintenance, they can reduce these pathogens to levels that are easily handled by the seahorse immune system.

Reactors can be useful in seahorse aquariums that have chronically high nitrate or phosphate levels. NP style bio-pellets in bio-pellet reactors are recommended for seahorses.

Rule #7: Watch Your Water Parameters

Seahorses are sensitive to low pH and high ammonia. Low pH can cause them to lose their appetites, and high ammonia can burn their sensitive gills and eyes and kill them rather quickly. They’re tolerant of nitrates, but it is still good practice to keep nitrates below 20 ppm because high organics can cause infectious bacteria to bloom. Seahorses need calcium to maintain their bony plates, so keep your calcium and alkalinity levels stable. Salinity should be stable and measured with a refractometer. Specific gravity can be kept between 1.020 and 1.025.

Young H. kuda on a gorgonia skeleton

Rule #8: Create a Seahorse-Friendly Aquascape

Dry Live Rock is perfect for seahorse tanks because it does not contain pests like Aiptasia anemones which can sting and irritate seahorses. Use a variety of shapes including branching live rock for seahorses to hitch on. Live fancy macroalgae can give your seahorses holdfasts as well as control nitrate levels. You may incorporate artificial decor into your aquascape, but make sure the materials are saltwater safe. Not all aquarium decorations are safe for use in saltwater.

This gorgeous male Bluestripe Pipefish is a challenge for reefkeepers and seahorse experts

Rule #9: Keep New Seahorses in a Species-Specific Tank

It is best to keep young, small or new adult seahorses in species-only tanks until they are mature and conditioned. Turn down the light intensity and flow in the display tank a bit while they are adjusting to their new environment. Once your seahorses have gone through quarantine and conditioning, are eating well and fully mature, and have adjusted to the display tank, you may add safe tank mates to the aquarium.

Rule #10: Be Mindful About Coral Compatibility

Seahorses are compatible with most soft corals like Zoanthus, Xenia, Cabbage leathers, Tree corals, Spaghetti Finger Leathers, Gorgonians, and small mushrooms. Compatible LPS are not able to consume a seahorse and do not sting. These include Tubastrea, Scolymia, Acanthastrea, Lobophyllia, Turbinaria, etc. Do not house seahorses with any species of coral that could consume the seahorse like Elephant ear mushrooms or LPS corals with large mouths. Stinging corals are extremely dangerous for seahorses. Never put anemones, Euphyllia, Galaxea, or other stinging corals with your seahorses. It is difficult to keep SPS corals with seahorses. Seahorse aquariums tend to have higher nitrate and phosphate levels than SPS corals prefer, and seahorses tend to irritate the SPS by hitching on them.

Euphyllia spp. like frogspawn, torch, and hammer corals are never safe tank mates for seahorses

Rule #11: Don't Forget About Fish Compatibility

Most fish are not good seahorse tank mates. Some obvious no-nos are triggerfish, puffers, large angels, sharks, aggressive wrasses, Eels, stinging fish like Lionfish, etc. Some seemingly peaceful fish like blennies and clownfish are also risky. Seahorses are not able to escape or defend themselves against attacks even from small fish. Young clownfish can be suitable tank mates, but once they reach maturity, their aggressive behavior poses a serious threat to seahorses. Always have a backup plan when you’re adding fish to a seahorse aquarium. Some fish can be model tank mates for months or years before viciously attacking a seahorse. Make sure you’re able to remove the offending fish if it becomes a problem. Don’t take unnecessary risks, as they usually end in disaster. Remember that your seahorses are more susceptible to some pathogens than other fish, so quarantine all new fish before introducing them to your seahorses to prevent disease outbreaks.

Fish that are always compatible with conditioned seahorses include tiny gobies like Clown, Trimma, Eviota, and Stonogobiops; Dragonets and Scooters; and small, peaceful gobies like Curious Wormfish and Eel Gobies.

War Paint Gobies are tiny, adorable, and peaceful additions to any seahorse tank

Fish that are usually compatible with large adult seahorses include Royal Gramma Basslets, very small Anthias species, Ecsenius Blennies, small Cardinalfish, Dartfish and Firefish, larger Watchman Gobies, small Jawfish, Flasher Wrasses, Assessors, and small Hoplolatilus Tilefish.

Pipefish and related species like Sea Moths are compatible with seahorses in terms of temperament, but remember that these are wild caught relatives of seahorses and can easily transmit pathogens to your captive bred seahorses. Many seahorse keepers opt to keep wild caught pipefish separate from their seahorses. If you choose to take the risk, make certain you are quarantining and de-worming your new pipefish for a minimum of 9 weeks before introducing them to your seahorses. This procedure is well documented online. Also remember that wild caught pipefish are difficult to keep in captivity.

Dragonface Pipefish are one of the few Syngnathids that do well in SPS tanks. They're often used to control Acropora pest red bugs.

Rule #12: Invert Compatibility Matters, Too!

Most small snails are great tank mates for any seahorse. Nassarius snails will help keep the tank clean by eating leftover food you may have missed while siphoning. Tiny hermit crabs are generally safe, but avoid larger crabs that can pinch and injure your seahorse. Clams and scallops can injure or trap a seahorse. Some sea stars and urchins are predatory, so use caution. Small shrimps like Sexy shrimp will be a snack for most seahorses, but medium shrimp like Peppermint shrimp are good tank mates. Avoid cleaner shrimp that may harass and stress seahorses. Large shrimp or lobsters pose a threat to seahorses. Porcelain crabs and small ornamental squat lobsters are peaceful and compatible with seahorses. Feather dusters and non-toxic filter feeding cucumbers are also safe.

Rule #13: Feed Seahorses a Varied Diet

Mysis shrimp is the best staple diet for seahorses. Spirulina enriched frozen brine shrimp contain high amounts of vitamin E and are recommended as treats a few times a week to prevent vitamin E deficiency and myopathy, but don’t have enough highly unsaturated fatty acids to be the main diet. Copepods are excellent nutritious sources of HUFA, but some adult seahorses may not notice them because of their small size. Experiment with different frozen foods to find out what your seahorses like so you can offer them a varied diet.

Rule #14: Vitamins Can Help Prevent Nutritional Deficiencies

Brightwell Aquatics AminOmega is a great HUFA supplement. It is so concentrated, it can even be used to raise seahorse fry. You can use this product to gutload live adult Artemia, or you can soak frozen food in it. Also adding vitamins to your frozen food will help prevent nutritional deficiencies.

Many seahorse keepers train their seahorses to eat from a feeding dish or large seashell. You can also use a product like the CPR Smart Feeder to target feed slow or picky seahorses. It allows you to place the food close to the seahorse instead of broadcasting it all over the tank to be picked up by the filtration or lost under rocks.

Rule #15: Conservation Status - Don't Believe The Hype

It is a common misconception that seahorses are endangered. Only one species of seahorse, Hippocampus capensis, the African cape seahorse, is endangered in its natural habitat because of pollution, habitat loss, and freshwater run-off. It is not common in the aquarium trade and no longer available for sale in the United States because of low demand. H. capensis is relatively easy to breed in captivity, but prefers cool water and requires a chiller. A few other species of seahorses live in very deep or remote places, so scientists are unable to assess the health of their population.

Today the aquarium trade has very little impact on numbers of wild seahorses. Most seahorses purchased for pets are now bred in captivity. All seahorses are protected by CITES because populations were in decline due to use in the Traditional Chinese Medicine Trade and the Curio souvenir trade.

Seahorse with a small lesion. Address injuries and infections immediately.

Rule #16: Stock Your Medicine Cabinet

Seahorse keepers are urged to have a “medicine cabinet” for their pets. When seahorses get sick, it happens quickly. Some infections can kill in 24 hours. You probably won’t have time to wait until after work to pick up medicine locally, and waiting a day or two for them to arrive in the mail is very risky. Having these medications on hand at all times will allow you to treat your sick seahorse right away and greatly increase their odds of survival. Make sure to replace them when they pass the expiration date!

Before using these medications on your seahorses, please consult a seahorse expert at Marine Depot, a seahorse group on Facebook, or a seahorse forum. These medications must be used in a quarantine or hospital tank unless otherwise directed. Always wear gloves when handling meds and changing water in your hospital tank.

Recommended Medications:

Antibiotics

• API Furan 2
• Seachem Kanaplex (kanamycin)
• Neosporin (yes, the human kind. Make sure it has no added ingredients)

Anti parasitic

• Seachem Metroplex (metronidazole)
• API Genereal Cure (metronidazole and praziquantel)
• API Super Ich Cure (malachite green and nitrofurarzone)
• Kordon Rid Ich (malachite green and formalin)

Emergency

• Methylene blue
• Kordon Amquel plus

Unsafe medications for Syngnathids

• Copper
• MelaFix

References

• Fusedjaw.org
• Seahorse.org
• Fishbase.org
• https://reefs.com/magazine/seahorses-and-vibrio/
• Seahorses & Pipefish Facebook group