Care
Cerianthus is a genus of tube-dwelling anemones with some 28 species currently recognised. These incredibly beautiful, but somewhat potent stingers do not have a pedal disc to anchor themselves in place like regular sea anemones, but instead live semi-buried in soft substrate. These animals have a crown of two whorls of distinctly different-sized tentacles (the two sets often in contrasting colour to one another), and live in a heavy, parchment-like, flexible tube created from threads of mucus and specialised secretions of nematocysts called ptychocysts. This casing surrounds the whole anemone up to the crown of tentacles, and oftentimes it ends up coated with sand, shell fragments, and other reef debris. The outer ring of tentacles are long and tapering, and are particularly well-armed with nematocysts, whereas the inner set of labial tentacles are much shorter and house the central mouth; these shorter tentacles aiding the anemone in pushing food towards the oral disc. If disturbed, the anemone retracts immediately into the safety of its tube, owing to the swift mechanism of the powerful longitudinal muscles located within the tube. The colouration of the tentacles is highly variable and may range from cream, beige, blue, orange, pink, purple, and green. In the confines of the home aquarium, Tube Anemones require a LOT of space around them due to their expansive size and the significant threat they unfortunately pose to other reef inhabitants, including corals and large tridacnid clams. Also requisite is a deep, soft/fine substrate (of at least 7.5cm/3" in depth) in order for the anemone to bury its tube adequately. Ideally there will be plenty of healthy live rock in the main tank, and a fishless refugium in which natural planktonic foodstuffs can be cultured on an ongoing basis. The Tube Anemone is not photosynthetic and does not require bright lighting; indeed, it is best placed in a dimly lit area of the aquarium to emulate the natural deeper habitat. Filtration/protein skimming should be efficient, but circulation should not be too brisk as it will hinder the feeding ability of these filter feeders. When tube mucus/stinging cells are expelled from time to time (usually obvious by the particles of sand adhering to it), it is best to siphon this from the tank as soon as possible. Tankmates are tricky: do not keep with any large, destructive fishes such as puffers, triggers, large angelfish, or large crabs/lobsters. Unfortunately, many smaller, peaceable tankmates are also not suitable because they are an easy target for the Tube Anemone, particularly overnight. Never attempt to house clownfish with Tube Anemones, as they do not have any kind of resistance to their nematocysts as they do with the true sea anemones. Some aquarists have had agreeable results with some of the more robust, larger damselfish species, along with Monos and Scats. Be aware that there is an element of risk for all fish that are housed with Tube Anemones though, and observe very carefully.
FeedingLacks zooxanthellae and needs to be fed well on small planktonic foods plus very finely shredded Mysis and vitamin-enriched brineshrimp. Never offer large items of food. As a largely nocturnal animal, be sure to target feed once the aquarium lights have dimmed and it has fully expanded. It may be necessary to temporarily shut off filtration/protein skimming whilst feeding to ensure your Tube Anemone is able to draw in sufficient food.
Propagation
Reproduction has been observed in the home aquarium, but none of the subsequent larvae made it through the transitional planula stage of development. When this event occurred, two individuals left their tubes and floated at the water's surface, swollen and with tentacles entwined. A few weeks later, the aquarist observed a mass of floating small pink-orange eggs. It is thought the tiny larvae succumbed through lack of appropriate foodstuffs.
