Caring for pet Seahorses


A featured image for a blog post on how to look after a seahorse pet

Southern Knight Seahorses (Hippocampus abdommalis) are temperate marine fish found in coastal waters of south-eastern Australia and also in New Zealand. Seahorses belong to the family Sygnathidae which has over 200 species (half of which occur in Australian waters.) This species is also known as the large-belly or Big-belly Seahorse. Seahorses are unique animals which make spectacular aquarium subjects.

They have a graceful manner, attractive colouration and are reported to live for up to 9 years in captivity.They also have an unusual prehensile tail which is used to hold onto seaweed or the substrate.

Male Gets Pregnant

Another unusual feature is that when Seahorses breed, the male becomes pregnant and gives birth to hundreds of tiny live seahorses! Their strange appearance has long fascinated mankind and many people still consider them almost as a mystical creature!

Southern Knight Seahorses are now being commercially produced in Australia, helping to ensure that wild stocks are not over-exploited. Being tank reared, these fish are surprisingly easy to keep. They are quite tolerant of varying water salinity and temperature, will eat frozen foods and come from a disease free hatchery. Being a temperate species, they can also be kept in an unheated indoor aquarium in most regions of Australia.

Easy to care for

Seahorses make a unique and interesting pet. Their added bonus is ease of care and that they are hardier then other marine species.

Basic Requirements

If you are about to get any marine fish, you need to make sure you have the basic requirements, before you even bring them home! Here is a list of the basic requirements for any marine aquarium.

  • Aquarium
  • Filtration (under gravel, corner or power filter)
  • Aeration (air pump & air stone)
  • Lighting (or natural light)
  • Heater
  • Substrate (gravel, sand, pebbles etc.)
  • Marine Salt
  • Food
  • Treated/Stabilized Water
  • Hydrometer & Thermometer

Optional Requirements

  • Filters
  • Aeration
  • UV Lighting
  • Ornaments
  • Plants (live or plastic)
  • Test Kits (pH, ammonia etc)
  • Aquarium Backing


Suitable For People Aged: 15 & over
Experience Required: Cold or tropical preferred
Feeding Care Time Required: 5 Min a Day
Maintenance Time Required: 2 Hours a Week
Minimum Space Required: Aquarium
Cost of Upkeep: (approx) $15 Per Week (Power Required)
Life Span: (approx) Up to 9 years
Availability: All Year


Can be kept in filtered aquaria, or in bowls as small as 10 litres. Two to four 7-10cm Seahorses can be housed in a 10 litre bowl with under gravel filtration. (A much larger aquarium is preferable in areas which receive a lot of summer heat). Fifty per cent water changes should be done each fortnight. (Seahorses require very well oxygenated water, so air uplifts are essential – standard air-driven under gravel filters are ideal.)

Substrate should be shell grit or crushed coral, or a 50/50 mixture of aquarium gravel and shell grit. Tank decorations should be added for the Seahorses to hang on to – well seasoned driftwood or plastic plants which are not too spiky are ideal.

Rocks can also be utilized.

Do not place live corals in with the Seahorses as the corals may sting and kill them within several days.

Seahorses are best kept without any other fish species, as their gentle nature does not allow them to compete for food.


Grows to 20-25cm in Australian waters, grows to 30cm in New Zealand in cooler conditions.


Colours can vary as Seahorses are able to mimic their surroundings. Usually white or golden, with variable dark spotting.


Southern Knight Seahorses soon adjust to temperatures within 12-28 C, with optimum temperatures being 15-22 C. Aquarium heaters are not required in most indoor situations.


Requires either seawater or artificial seawater, salinity range: 15 ppt to 36 ppt (1.0 to 1.02 specific gravity). When preparing artificial seawater, ensure the water used contains no chlorine.

pH: preferably 8.2 – 8.4, do not exceed 9.0.

Do not use aquarium water that has previously held other fish or invertebrates.

Although Seahorses are quite tolerant to ammonia and nitrite, their biological filter will still need to fully establish before the tank is fully stocked.


Southern Knight Seahorses have been trained to eat frozen brine shrimp. At temperatures below 20 C, feed each Seahorse 20-25 brine shrimp once a day. At temperatures over 20 C, feed this amount twice a day.

Will also eat small frozen krill, live black worm and live brine shrimp. In time Seahorses will learn to eat flake food, if they are fed a mixture of frozen shrimp and ground flake food. Ensure no uneaten food remains in the aquarium.


Southern Knight Seahorses begin breeding at 4 months of age. Males can be recognized by their belly pouch, they actually inflate the pouch to its’ maximum extent to try and impress potential mates. During spawning females transfer their eggs to the male’s pouch where they are nurtured for about 30-50 days, depending on temperature. Large specimens release broods of 300-400 fry. In the wild, males release 3 or 4 broods over summer. The male’s pouch is white and darkens in colour as the eggs develop. Newborn fry are about 21mm long and can be fed on live baby brine shrimp.


These seahorses are regularly checked to ensure they are in good health. The key to their well being 1s good water quality and good food, (particularly when kept in small aquariums or bowls).


Before unpacking, please check temperature of both shipping water and future holding tank.

Please note:

*If the tank is warmer than the shipping water, lower the temperature by adding ice. (Party ice is ideal as it is chlorine free). The effect of the ice on salinity will be negligible.

When the temperatures have equalized, release the Seahorses. The aquarium water temperature will then gradually return to its previous temperature.

*If the holding tank is colder than the transport bag, float the unopened bag for 5 – 10 minutes or until the temperatures equalize, before releasing the Seahorses.


Southern Knight Seahorses make a fascinating and enjoyable pet. They quite easy to keep – if given a few simple requirements such as filtered regular water changes and frozen food.