The Fighting Conch is an excellent sand sifter for DSB tanks. It doesn't grow as fast as the Queen Conch, but each one needs two square feet of sandy surface area to get enough to eat. On occasion it will bury itself completely in the sand to where one eye stalk is all you can see, and may not resurface for weeks. This is normal, and perhaps that is its growing period. They jump quite high with a very powerful foot. The snout extends across sand and glass, but never on the rockwork.
Hand-carried from the Florida coast, this Crown Conch was added to my refugium (8/11/03). Fortunately I took a few pictures, because it immediately buried itself in the sand. My Fighting Conch does the same thing for up to two weeks at a time, so I'm not too concerned. I love the shape of the shell, and how it glides across the sand like a hovercraft. Approx. 2.5" in length. It is very likely a carnivore, and it lived for a few years in my system. Not Reef-safe.
This tiny Cowrie is the size of an olive. It lived in a display tank at the local fish store for months amongst many corals, and did no harm. Since some cowries are herbivores, I decided to add it to my reef to consume any filamentous algae that it might find. It has a soft skin or mantle that extends over its shell when it feels safe. Reef safe.
A fellow reefkeeper took this picture: It is a Cirolanid Isopod, a very tiny creature that feeds on fish similarly to ticks on dogs. Usually these appear affixed to the body of a fish, or gills. Do some research on how to remove them - they are unwelcome pests. If left unchecked in your tank, fish will die. You will need to leave your aquarium fish-less for 2 to 4 months to erradicate these. NOT Reef-safe.
Many people ask about a snail or slug with a half-shell on its back. This one is a little different, as it is a black Stomatella, a fast moving slug. This one is pictured with a few spirorbid worms on its back, making it a little more unusual. (This is the more common Stomatella.) Their shell is similar to a fingernail in shape, which covers the head and torso of the creature.
Pods? What are pods? They are tiny little bugs that fish consume as part of their normal diet. Mandarins, Wrasses and more enjoy these delicate crustaceans. In a well established refugium, you should see many pods scurrying around. This is anAmphipod, which is recognized by its shrimp-like shape. Copepods are straight in shape, and look like tiny bugs. Amphipods are much easier to see. Reef-safe.
Fighting or Sand Conchs stir the sandbed, keeping it clean. This is a helpful clean up crew creature that tends to stay on the sandy substrate looking for food. It may bury itself for days at a time, only to emerge a bit larger (shell-wise) and ready to work. Usually it is best to add one per every two square feet of available sand area.
Nassarius snails are an excellent snail for keeping the sand stirred up. They tend to hide, although you may spot their feeding tube extended up slightly like a periscope. When food hits the water, they quickly emerge completely and move quickly about the substrate.
Nassarius snails can breed in a tank, but their eggs rarely hatch out and turn into baby snails. The fish pick them off like caviar. This is their laying pattern, something that can be identified easily.
Here's another picture I took at a local fish store. I always look for opportunities like that. :)
When it comes to keeping algae in check, the Margarita Snail - Margarites pupillius - is a great choice. The shell is dark grey or black, and rounded over. They do quite well in reef environments, and even when flipped over can right themselves and continue on their way. Reasonably priced, adding these is a great plan. Hermit crabs aren't interested in their shells, so they are safe from predation. Reef-safe.
Once, I discovered these beautiful Red Footed Snails at the LFS. They are also called Mexican Red Foot or Norrisa Top Shell, and are reported to consume green hair algae and cyano bacteria. Why don't we all have these?!? Somewhat expensive at $5 each, they do better in cooler water (around 72F) so life expentancy will be short in tanks running tropical temperatures (78-81F). The bright red is a real eye catcher, contrasted by a black mouth and white foot.