Description

The Southern Knight Seahorse, scientifically known as Hippocampus abdominalis, is also commonly called the Pot-bellied Seahorse or Big-belly Seahorse.

Key Facts:

• Distribution: This is the largest seahorse species found in southeastern Australia and New Zealand. Their habitat ranges from the Three Kings Island in the north of New Zealand down to the Snares Island in the south. In Australia, they are found from Sydney southwards and west to the Great Australian Bight.
• Habitat: They typically inhabit shallow coastal waters, including bays, estuaries, and sheltered coastal reefs. They are often found in seagrass beds and macro-algae (like Cystophora and Sargassum). Juveniles may attach to drifting seaweed. They can be found in depths ranging from the intertidal zone down to at least 50 meters (160 ft), and occasionally even deeper.
• Appearance: They have a distinctive pot belly, a long snout, and a long, coiled tail. Their coloration can vary, including yellow, brown, or white, often with dark spots and stripes. They can change color to blend in with their surroundings. They lack scales but have bony plates. Males have a prominent pouch on their abdomen for carrying eggs. They can grow up to 20-25 cm (8-10 inches) in Australian waters and even larger, up to 30-35 cm (12-14 inches), in the cooler waters of New Zealand.
• Temperament: Southern Knight Seahorses are gentle and peaceful. They are not strong swimmers and rely on their prehensile tails to anchor themselves to seaweed or other structures.
• Diet: They are carnivores, feeding on small crustaceans like amphipods, copepods, and brine shrimp, which they suck up with their long snouts like a vacuum cleaner. They lack teeth and a stomach, so they need to eat frequently. In captivity, they can be trained to eat frozen foods like mysis shrimp and plankton.
• Tank Requirements (for aquariums):
  • A taller tank is preferred due to their vertical posture. A minimum of 40 liters (10 gallons) is recommended for a few seahorses, with at least 50 liters (13 gallons) for an adult pair.
  • Water temperature should be kept between 15-21C (59-70F). In warmer climates, a chiller may be necessary.
  • Maintain a pH of 8.0-8.4 and a specific gravity (SG) of 1.020.
  • A gentle filtration system is needed. Avoid strong currents.
  • Provide plenty of hitching posts like artificial or live plants, corals, and rockwork.
  • A sandy substrate is suitable.
  • They are best kept in a species-only tank or with other very peaceful, slow-moving fish like pipefish or some gobies and dragonettes that won’t compete for food. Avoid aggressive or fast-moving fish.
• Breeding: Seahorses have a unique reproductive process where the male carries the eggs in a pouch. The female deposits her eggs into the male’s pouch, where they are fertilized and incubated for about 30-50 days, depending on the temperature. The male then gives birth to live young (fry). They can begin breeding at around 4 months of age.

Southern Knight Seahorses can live up to 9 years in suitable conditions. They are a fascinating species often kept in aquariums, and those available are often captive-bred, making them more accustomed to aquarium life and frozen foods.