Aquarium Set Up

Aquarium Set Up

Despite what some people believe, keeping a captive-bred seahorse in an aquarium is not difficult. Like most marine fish, it may be time consuming.

After all, they are a live animal that needs to be cared for appropriately. We recommend that you read up a bit before purchasing so you know what you are doing. Beware, there are still some wild-caught seahorses on the market and they can be more difficult to look after, as they need live food; this is perhaps where some people have got the impression that they are hard to keep.


Captive-bred seahorses are fun to keep in an aquarium but like any pet, they need to be fed appropriately and their environment maintained. You should look into what is required before purchasing your seahorses, keeping in mind that requirements may vary between species.

You can make your aquarium as simple or as elaborate as you desire. There are literally thousands of accessories on the market and it can be daunting at first. Below is a guide for setting up a seahorse aquarium. If you have any questions, feel free to contact us here at the farm or for more detailed coverage you can purchase a book in the seahorse shop.

Choosing a species

Temperate, tropical and sub-tropical species are available. Temperate species, which require cooler water temperatures (e.g. 16-20 C) should only be kept in cooler climates or where other methods of water cooling, such as a chiller, are available. Similarly, a heater may be required for tropical species.

Size should also be considered. Larger species such as Southern Knights or Asian Emperors require larger aquariums. Southern Champions are a small species and can be kept in smaller tanks. Our current range of captive-bred seahorses is found in the seahorse shop.

Choosing a tank

There are many different sizes and styles of aquaria to choose from. An expansive aquarium will help you to observe the fascinating habits of your seahorses.

The minimum size should be about 50L (see individual species pages), which will safely house two seahorses up to about 14cm in length. Larger fish should be given a minimum of 80L per pair. However a larger tank (e.g. 150L) will allow you flexibility in interior design, while giving the seahorses room to explore their habitat. Deeper tanks are desirable if you intend to breed your seahorses (see Breeding).

The larger your tank, the easier it is to maintain optimum water quality

Substrate and Filter

There is a vast array of filter systems available on the market. Internal Powerhead filters are great, though it’s important that you choose a size appropriate for your particular tank. Ideally, you want the whole volume of your aquarium to pass through the filter 3-4 times each hour. Eg, for a 90-L tank, choose a Powerhead that filters 270-360 litres per hour. A common mistake when using a Powerhead as the sole means of filtration occurs when cleaning. Beginners will be tempted to clean all the filtering materials even though this destroys much-needed biological filtering capacity. It is pertinent to clean only some of the filter material at a time. See your local aquarium dealer, or contact us at the farm for further details.

Undergravel filters are commonly used in aquaria where they act as both a mechanical and biological filter. These filters are usually inexpensive and work very well, though are the most laborious to maintain. A simple undergravel filter consists of a base-plate on which 3-5cm of coarse washed pebbles are placed. Please avoid very small stones, sand or shell grit as there is some risk that these may be ingested by the seahorses while foraging for food. Scattering larger stones on top of your pebbles makes a great looking tank. These filters are usually driven by air and therefore help to keep the water well saturated with oxygen.

External Canister filters are more elaborate and expensive, they work great (be sure to choose the right size for your tank) and are the easiest to maintain.

Large tanks may incorporate more than one filter. For the best system for your needs and budget consult your local dealer or contact us at the farm.

Air Supply

When setting up air-stones, be aware that excess air can be problematic, as the male seahorses can get air trapped in his pouch. Seahorses love to sit in the stream of bubbles coming from airstones. Occasionally, a male may get some air trapped in his pouch (this can also occur during courtship with a female). This can be easily remedied by a gentle squeeze:

1. Wash hands thoroughly and ensure there is no soap or moisturiser residue.

2. Hold your male in both hands, just under the water surface, with his pouch-opening upwards.

3. Starting at the base of the pouch, very gently squeeze from the bottom up, encouraging him to open his pouch and release the air. It may take 3 or 4 attempts. Be patient, he will thank you for it.

Holdfasts and Corals

Some artificial branches or other structures should be added that provide sites for the seahorses to wrap their tails around. Rope and netting are fine or choose artificial ornaments from your aquarium shop that have suitable structures for the seahorses to wrap their tails around. Avoid items with sharp edges. Live corals require temperatures outside the range of temperate species, and therefore are not compatible inclusions. For the tropical species some corals are safe but others emit toxins so corals may not be the best additions if you are unsure. Some claim that Chargers are the best suited species for aquariums with corals. Take care if adding live rock to your tank as it can be a source of harmful parasites. See " Tank Companions " for other great temperate marine animals that complement Southern Knights and Southern Champions.

Biological Filtration & the Nitrogen Cycle - Looking after your water quality

Biological filters are a normal part of keeping any aquarium. Your biological filter (which is your pebbles/substrate in an undergravel filter, or your sponge and noodles in a suspended Powerhead filter) is designed to grow helpful bacteria, which convert toxic products (excreted from fish), into non-toxic forms.

Fish excrete ammonia, which is toxic if it accumulates. One species of bacteria in your biological filter feeds on the ammonia and converts it into nitrite.

Nitrite is also very toxic, however another species of bacteria will convert this to nitrate.

Nitrate is much less toxic to marine fish, and can be removed with the help of a simple protein skimmer, and by renewing some of the water. (Nitrate is an excellent nutrient for plants, so high levels will encourage algae growth).

While providing adequate food for your seahorses is necessary for their health, overfeeding is dangerous for 2 reasons:

1. It encourages the growth of ‘unsafe’ bacteria 2. Levels of ammonia, nitrite and nitrate may rise suddenly to dangerous levels ("spike")

As with all aquarium fish, overfeeding should be avoided at all times. Any uneaten food should be removed to avoid poor water quality.

Levels of ammonia, nitrite and nitrate can be easily tested with test kits, available from pet-shops or the Seahorse Shop.

Ideal levels are:

Total Ammonia at Zero mg/L
Nitrite at Zero mg/L
Nitrate at or below 100 mg/L

So, how does your biological filter become established?

Any type of fish will excrete ammonia, and this is what is needed to begin growing the bacteria in your biological filter. However, in a new tank, the ammonia will rise to dangerous levels before there are enough bacteria to break it down. Therefore it is highly recommended that you establish your biological filter prior to stocking with seahorses. There are several ways to do this – the two most popular ways are:

1. To use bottled culture media (from your pet shop)
2. To set up your tank and put in a prawn or some frozen fish food. As the bacteria break it down, they will produce ammonia and kick-off the biological cycle. If you regularly test your water during this period you will see ammonia levels peak, followed by nitrite levels peaking, then ammonia falls to zero followed by nitrite levels.
Note: live rock can also be used but be aware that various animals living in live rock, such as crabs, can hurt seahorses.

The cycle can take 4-6 weeks to complete. You will know it is complete because your ammonia and nitrite test will show readings of "zero". This means the bacteria are living in balanced numbers.

You can now consider your tank to have 'cycled' and confidently add your seahorses.

Water Quality

When you first set up your aquarium and add your seahorses, it is wise to check the following parameters regularly: temperature, pH, salinity, ammonia, nitrite and nitrate. When the readings are staying relatively stable, you can stop checking so often and sit back and enjoy your extraordinary new pets.


Salinity tolerance is likely to vary between species. Southern Knights, which sometimes live in estuaries, tolerate a range of salinity from a minimum of 18 parts per thousand (ppt) to a maximum of 36ppt but living conditions below about 25ppt should be promptly corrected. About 32 ppt is ideal; in specific gravity terms, between 1.01 and 1.02. Measuring salinity is done with an inexpensive hydrometer, which is readily available from your aquarium dealer and from our Seahorse Shop.

Preparation of Artificial Seawater

Using artificial seawater is a popular way of keeping marine fish. These days, commercial brands are available (an excellent brand is Ocean Nature, available from our Seahorse Shop).

DO NOT use a mixture of table salt and freshwater, as this will kill your seahorses!

Preparation requires care and we advise that the tap/fresh water be prepared first.

The following procedure is recommended:

1. Place fresh water in storage bucket. Dechlorinate carefully by adding water purifier. Aerate.
2. Wait for 2 hours
3. Add aquarium salt as per directions on the pack.

As time goes by, and particularly in warm weather, the salinity of your tank will gradually increase. Monitor and add fresh water (with purifier) to reduce the salinity level. Party ice is ideal to lower the temperature and salinity.


Seahorses inhabit temperate, sub-tropical and tropical regions around the world. This environment should be mimicked in your aquarium. Before deciding on what species of seahorse you would like, ensure that you check their temperature requirements and whether you are capable of maintaining that temperature. A thermometer is an essential aquarium accessory.

Refer to species descriptions for optimal temperature ranges.

Ideas to keep your water temperature down in warm climates:

  • Keep in an air-conditioned or cool part of the house.
  • A generous tank size (eg >80-L).
  • 2 freezer blocks. Keep one in the tank and one in the freezer and alternate as required.
  • Add party–ice. These simply replace evaporation and do not severely alter salinity.
  • Insulate unseen sides of tanks. (e.g. add polystyrene to sides of tanks hidden in cabinets).
  • Turn your aquarium light off in hot weather.


Having to find a source of live food is a thing of the past, thanks to captive-bred seahorses being trained to eat frozen food. They love frozen Mysid shrimp, small krill and brine shrimp. They require feeding twice per day with approximately 50 shrimp/krill. A sole diet of frozen brine shrimp is not recommended in the long-term, as it lacks important nutrients and your seahorses may slowly lose condition. It is best to supplement their diet with frozen Mysid shrimp or krill, as these have fantastic nutritional profiles.

As with all aquarium fish, any uneaten food should be siphoned away. When doing this, be careful not to injure your seahorse with the suction of the siphon.

If live diets are available from your aquarium dealer, these can be purchased occasionally to give your seahorse a treat. They will especially love the thrill of chasing their prey.

Disease Management

The key to good health is water quality and nutrition!

Our seahorses are regularly checked at the farm for any disease or health issues. Our staff ensures the good health of every fish leaving the farm. We do not recommend the indiscriminate use of antibiotics since resistant strains of bacteria may quickly result.

If you suspect your seahorse might be unwell at any time, the best immediate attention you can provide is to lower the temperature towards the lower end of its preferred range (e.g.16-18°C (65-68°F) for Southern Knights). Anti-bacterial agents can be administered if warranted, though be sure to dose your tank as per directions on the bottle, and continue the treatment for the duration of the organism’s life cycle.

More Information

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