Vermetid snails

Identification

A hard, irregular calcareous tube cemented to rock, coral skeleton or equipment, usually a few millimetres wide for the common small species and up to about 1 cm for large species. The tube often ends in a raised, slightly coiled opening with a dark operculum. The giveaway sign is a stringy mucus net or web cast out from the tube after feeding, which is then hauled back in and eaten. Colonies can cover rock surfaces, sumps, overflows and plumbing.

Often confused with

Tube worms and feather dusters, which wave a feathery fan crown from the tube; a vermetid shows two short antennae and a mucus net instead of a fan. Also confused with spionid worms, which show exactly two thin palps from a much smaller hole in coral or rock and never build a thick, raised calcareous tube.

What it targets

No direct host. The mucus nets drape over neighbouring corals, especially SPS and LPS bases, causing polyp retraction, lesions and reduced growth, and the sharp tubes compete for space on rock and coral skeleton.

How it spreads

Hitchhikes on live rock, coral frag plugs and colonies. Adults stay fixed for life; free-swimming larvae settle nearby, so numbers build up steadily in nutrient-rich tanks with plenty of suspended particulate food.

Control (safest first)

Manual crushing and removal at the base: break the whole tube off with bone cutters or pliers and dig out the base, because snapping off only the tip leaves the animal alive deep in the tube to regrow. Most reliable for small numbers; tedious at plague scale. Seal the tube opening with a dab of cyanoacrylate gel or reef epoxy putty: cheap and targeted for scattered individuals, although keepers report some snails boring a new opening beside or through the seal, so recheck sealed tubes. Reduce suspended food: lighter particulate and coral feeding, good mechanical filtration and water changes slow reproduction by starving the filter-feeding nets. Slow and partial on its own; established adults persist for months. Coral snow type clarifying treatments: some keepers report sharp population drops after repeated use, others report no effect at all, so treat this as an unproven adjunct rather than a cure. Biological help from bumblebee snails and some crabs or wrasses: hit-and-miss and species dependent; several keepers found predators only reached the snail after the tube was cracked open for them. Bumblebee snails may also prey on other small snails.

Natural predators

• Bumblebee snail→
• Emerald crab→
• Yellow coris wrasse

Field notes

Keepers split sharply on bumblebee snails: some stocked dozens in a large tank and watched the small vermetid species disappear over about two months, while others with the large tube species saw the snails ignore them completely until tubes were manually cracked open. One keeper with a heavy infestation tried glue, putty, coral snow and ozone, reported the snails persisted through all of it, and chose to live with them after noticing the corals still grew; a copperband butterfly in that tank learned to follow the keeper's hand at cleaning time to eat snails exposed by crushing. Another keeper reported an infestation fading away over roughly nine months in a holding system after broadcast feeding of the corals simply stopped, crediting food restriction and time rather than any predator or chemical.