I prefer snails and shrimp with NO hermits (little devils). I've heard anywhere from 1 to 5 per gallon. I think 1 per gallon is about right with the majority being nassarius snails, followed by cerith snails.
Astrea Snail-most common of all saltwater tank snails. They are excellent algae eaters and will forage all over the rock, sand, and glass. These guys fall very easily and can not right themselves up and die easily.
Banded Trochus Snail - Large snails that are excellent algae eaters although are very slow about it. These guys have a hard time picking themselves up as well if stranded in the middle of the sand.
Bumblebee snails- Not very hardy. Marginal algae eaters, but more of a detritus grazer. They can prey on other snails and sand bed critters.
Cerith Snails (Cortez) - Good algae and detritus eaters that forage rock, glass, and sand. Some can pick themselves up and some cant.
Cerith Snails (White)- Good algae and detritus eaters that seem to stay in the sand more than the cortez, but can be found on the rock and glass. Once again, some can pick themselves up and others cant. These guys are good sand bed snails to shift the substrate around.
Fighting Conch Snails - These guys are all about the sand bed and are very cool to watch. They usually dont get flipped over, but if they do, they can kick around and turn themselves back upright.They very hardy too. One per 2 sq. ft. of sand.
Mexican Turbo Snails - super fast grazer that will knock out some algae in no time. They mostly stay on rocks and glass, but will work the top of the sandbed too. These may be cold water snails that dont do so well in a reef. But, once they are adjusted... they seem to be very hardy and active. Mine are going on two years and are huge now. I originally got them for a hair algae problem. They do tend to knock over anything that is not glued in place (corals, clams, rocks, etc.)
Nassarius Snails - They mostly stay in the sand, but will sometimes make short trips up the glass. They are mainly detritus eaters and do an excellent job cleaning and shifting the sand. I think these are also some of the most hardy snails out there. These guys can flip themselves upright very easily and quickly. They are fun to watch as they come bursting out of the sand bed at feeding time.
Nerite Snails - Mostly a rock and glass snail that are all about the algae. The dont move very fast but the areas they have been in are clean as a bell. These guys like to crawl out of the water. Mine usually end p in the sump where they can get above the water line and come back down when they want to.
Stomatella Snails - They are supposed to reproduce very well. No personal experience w/ them.
Strombus Snails (Strombus maculatus (sp?))these are excellent snails that reproduce very well. They seem to be mostly sandbed snails and will occasionally make there way up to about the 1-3 inch line of rock work. I assume they are mostly detritus eaters.
