Fish & Invertebrates

Turf algae has a grip on the back rock, the kind of short, tough fuzz that snails slide right over. You want something that will grind it down without bulldozing the tank. A small reef urchin, tucked into a crevice by day and grazing at night, is the animal our calculator reaches for first. Looking…

You drop a pellet in after dark and a thin red arm comes out of a hole in the rock, wraps it, and pulls it back in. You had forgotten you even owned a brittle star. That is how a good one behaves: out of sight, working the parts of the rock nothing else reaches.…

The sand looks empty. Then a pellet sinks, and within a minute a dozen thin siphons pop up out of the bed, followed by small shells racing toward the food. That is a nassarius crew, and it is half the reason people keep them. Looking for them now? See the nassarius snail singles and the…

For the first week you hardly see it. By day it is wedged under a ledge with two thick spines showing. After lights out it is on the open rock, grinding through film and turf in slow circles. A slate pencil urchin is a night shift worker, and its blunt spines make it the easiest…

You leave for a long weekend and come back to find a shell, two pieces of rubble and a small frag plug stuck to the top of your urchin, which is now on the other side of the tank. That is a pincushion urchin doing exactly what it does on the grass flats here, and…

Lights go off, and an hour later you shine a flashlight into the tank. The glass right at the sand line, the strip you can never reach with a magnet, has a row of narrow spiral shells working along it. Those are ceriths, and that strip is one of the jobs they do better than…

You bought a pack of hermits and a pack of snails on the same day. Three weeks later you count empty shells on the sand and a hermit wearing a shell that used to belong to a snail you paid for. If that has happened to you, the scarlet reef hermit is the hermit to…

A few green bubbles show up on a rock in the back corner. A month later there are thirty of them, wedged where tweezers will not reach. That is the moment most people buy an emerald crab, and it is a reasonable move as long as you know what the crab will and will not…

Your sand bed looked white the week you set it up. Six months later the top layer is tan, packed flat and dusted with film algae, and the nassarius come up to eat and go straight back down. That top inch is the job a fighting conch does all day. Looking for one now? See…