Common name: sand fish

General information

Holothuria scabra, commonly known as the Sea Cucumber or Sandfish, is a species of sea cucumber found in tropical Indo-Pacific waters. It is a benthic organism, meaning it lives on the seafloor, and is well-known for its role in nutrient cycling and sediment turnover. The Sandfish has a leathery skin and an elongated body that can reach up to 40 centimeters in length. Its coloration varies from dark brown to black, helping it blend into its surroundings.

Care

In the aquarium, Holothuria scabra requires a large tank with a deep sand bed to mimic its natural habitat. It is a detritivore, feeding on organic matter within the sand, which it processes to maintain a clean and healthy substrate. The Sea Cucumber should be kept in a system with stable water conditions and low to moderate flow. It is sensitive to high levels of nitrates and sudden changes in water parameters.

Reproduction

Sea Cucumbers have a unique reproductive strategy known as broadcast spawning, where males and females release sperm and eggs into the water column. In the aquarium, breeding Holothuria scabra is challenging due to the need for precise environmental cues and the difficulty in raising the planktonic larvae.

Symbiosis

Holothuria scabra has a symbiotic relationship with various microscopic organisms that live on its skin and within its gut. These symbionts help in breaking down the organic matter that the Sea Cucumber consumes. While not as visually striking as clownfish-anemone symbiosis, this relationship is crucial for the nutrient cycling in reef ecosystems.

Habitat

The natural habitat of Holothuria scabra ranges from shallow lagoons to reef flats and seagrass beds. They are often found partially buried in the sand during the day. Their geographical distribution spans from the Red Sea and East Africa across the Indian Ocean to the Western Pacific.