News / Species Spotlight / Revisited: Trochus Snail (07/16/15)

Revisited: Trochus Snail

Trochus Snail

Scientific Name: Trochus niloticus
Common name: Trochus snail, Top snail

  • Class: Gastropoda
  • Order: Vetigastropoda
  • Family: Trochidae
  • Genus: Trochus
  • Species: niloticus

The Top snail (Trochus niloticus) is one of the most popular and biologically important gastropods in the world. While this article will focus on a specific species, there are a number of snails in the Turbo, Astraea, Tectus and Trochus genera that fall into this category. T. niloticus grows to 4 inches and is commonly referred to as a top snail, due to its conical shape. The adult shell is typically covered in coralline algae, but has distinctive dark red stripes. The shell is smooth and heavy with a thickened, spreading peripheral end. The body whorl has concave sides. It provides food for islanders, as well as a source of jewelry and buttons with its magnificent mother of pearl interior luster. Trochus spp. have been commercially harvested since 1900 and it is estimated that 3000-6000 tons of Trochus spp. are harvested each year for shell products and meat, making it the most valuable of any marine snail. An interesting fact about Trochus spp. is their ability to release toxins into the water in order to avoid predation. It is believed that T. niloticus lives for 8-10 years in the wild and much is still unknown about their ecology.


T. niloticus natural distribution ranges from the Andaman Islands in the Indian Ocean to the Pacific islands of Fiji and Wallis, including Palau, Yap, Papua New Guinea, the Solomon Islands, Vanuatu, and New Caledonia, and the north and northeastern coasts of Australia. They have been introduced extensively throughout the Pacific where they are now commonly found. T. niloticus can be found in the littoral (surf) zone foraging on turf algae in tropical and subtropical seas. Its primary diet consists of various macroalgaes, as well as diatoms, cyanobacteria and detritus. T. niloticus spawns near the new and full moons and will come to the surface of the exposed reef to release its sperm and eggs. The mariculture of T. niloticus has been successful due to the fact that the eggs are lecithotrophic (contain large amounts of yolk), resulting in planktonic larvae that do not need to be fed. The planktonic larval phase is short (2 to 8 days depending upon temperature). Once the larvae metamorphose and settle to the bottom of the tank, they feed on the benthic diatoms, and later the algae that grow spontaneously in the presence of artificial illumination or sunlight.

Aquarium Care

T. niloticus is a critical living component of the balanced reef aquarium. Together with sea cucumbers, sand conchs, serpent stars, hermit crabs and other janitors, top snails help to keep the rock and glass surfaces clean. It is recommended that you have one snail for every 5 gallons of tank water. Although T. niloticus can grow quite large, they are commonly available much smaller and grow slowly in the aquarium. They tend to be hardier than other snail species and acclimate readily. It should be noted that if you do experience a temperature spike in the aquarium (higher than 88 F), it is probable that T. niloticus will spawn after the aquarium returns to a cooler temperature. This is common with many mollusks, including giant clams. If spawning occurs, water changes may be needed if there is a high density of spawning animals. There have been some reports of larvae surviving to adults in aquariums with no special care, although this is rare. No special feeding is needed, as typical reef aquarium illumination will promote the growth of necessary diatoms and algae for their ongoing nutritional requirements.