Horned Nerite Snail

Species: Clithon corona.

Size: small, about 2 cm across.

Water: 22–27 °C, pH 7.2–8.2, moderately hard to hard.

Eats: algae and biofilm; only dead or decaying plant matter.

Breeding: lays eggs that will not hatch in fresh water.

The horned nerite is the smallest nerite we sell and the most unusual looking, with a row of short dark spikes standing up along the shell's edge. Colour varies from individual to individual: most are patterned in black and yellow or olive, which is why it is also sold as the bumblebee horn snail. It is recorded from Guam and the Philippines and probably ranges more widely through the western Pacific, living where rivers meet the sea.

It does the same work as the larger zebra nerite: it grazes algae and biofilm (the thin living film of bacteria and microscopic life that coats every surface underwater) from glass, rock, wood and leaves. Because it is small it fits into corners, between stones and along the fine stems that a bigger snail cannot reach. It eats only dead or decaying plant material, so slow-growing plants such as Anubias are grazed clean rather than damaged.

Like all nerites, females lay trails of small hard white eggs on hard surfaces. The larvae need brackish water (a mix of fresh and sea water) to develop, so in a freshwater tank the eggs never hatch and numbers stay exactly where you set them.

Water: 22–27 °C and pH 7.2–8.2, in moderately hard to hard water (about 10–25 dH, the measure of dissolved calcium and magnesium). The calcium keeps the shell and its horns solid; in very soft water shells erode.

Tank: best added to a tank that has been running for a few months and carries some algae. A lid without gaps matters, because nerites climb above the waterline and can leave the tank.

Feeding: if the glass is spotless there is little for it to eat, so offer an algae wafer or a small piece of blanched vegetable now and then, and remove leftovers after a day.