Unicorn Snails (Subulina octona)

This one is not an isopod. Subulina octona, the Unicorn Snail, is a small tropical land snail, and I keep it because it does a quiet, useful job that few other animals its size can manage. It is a tiny cleanup animal for bioactive setups and nano tanks, named for its elongated, spiralled shell that tapers to a fine point like a little horn. Where the isopods trundle through the substrate, this snail grazes the surfaces, and the two work happily side by side.

It is a small animal and stays that way. Adults reach 1.5 to 3 cm of shell, though most settle around 2 cm, with eight or nine glossy, semi-translucent, yellowish-brown whorls. The pale body can stretch almost as long as the shell when the snail is exploring, and through that translucent shell you can often see what is going on inside, including eggs developing before they are laid. Compared with the rounded, dome-shaped shells of most familiar snails, or my substantial Giant African Land Snails, the awl-shaped Unicorn Snail is an entirely different silhouette.

What it offers is quiet, constant work. Subulina octona is a detritivore, grazing decaying leaves, fungi, lichens and the biofilms that build up as an enclosure matures. In a planted terrarium or bioactive vivarium it processes waste before it accumulates, filling a slightly different niche from a springtail culture or a colony of isopods. It is peaceful and safe with most inverts, small enough not to compete with them and unbothered by their company, which is why so many keepers add a few to existing tropical setups. They also make handy feeders for keepers who want a small, self-renewing food source.

Care is simple if you keep it warm and damp. These are tropical animals, comfortable at 20 to 26°C and happiest for activity and breeding nearer 24 to 27°C, with humidity kept high at around 80 per cent or more. Give them a few centimetres of moist, organic substrate that always feels damp to the touch. A little flake soil mixed in adds texture and nutrition, and a generous layer of magnolia leaf litter gives them both food and grazing surfaces.

Feeding is straightforward. Alongside leaf litter, they take soft vegetables sliced thinly and a pinch of fish flake, and they will graze biofilm on their own as the setup settles. The one thing I would not skip is calcium. Almost all of a snail's shell is calcium carbonate, so a piece of cuttlebone left in permanently, or some crushed eggshell, keeps the shell strong rather than thin and fragile. A small animal with a delicate shell needs that steady supply more than a larger, robust species does.

One thing to know before you start. Subulina octona is very prolific. Every snail is a hermaphrodite and can reproduce alone through self-fertilisation, so a small group becomes a large one quickly, and a starter handful can turn into dozens within a few months. For feeders and cleanup that is the whole point, but if you would rather hold the numbers steady you will need to remove eggs from time to time. Their tiny size makes all of this easy to house, and a group is content in a nano enclosure of only a few litres.

Every order is captive-bred from an established culture, boxed double-walled around a ventilated tub of damp sphagnum and posted Monday to Thursday by tracked next-day Royal Mail, with a live-arrival guarantee and a small overcount as standard.