That Fish Blog – Aquarium Advice and Information

Hello, Frank Indiviglio here.  I’m partial to snails…from tiny stream dwellers indigenous to the spray zone of one waterfall in NY to the huge lumbering African land snails, all that I’ve worked with have been fascinating.  But aquarists often have a love/hate relationship with snails, searching for one that will consume unwanted algae while not eating plants or over-populating the tank.  Enter the olive nerite, a/k/a black marble or Alexander snail (Vittina usnea, formerly Neritina reclivata alexandre).

Natural History

Amazingly, this adaptable snail, native to brackish water habitats in Florida and throughout the Caribbean and Gulf of Mexico, thrives equally well in fresh, brackish or marine aquariums.  It will, however, only reproduce in brackish or marine waters, and so is an ideal choice for freshwater aquarists who fear snail population explosions. 

In the wild, the olive nerite ventures far up rivers, often being found miles away from the sea.  It seems unlikely that such a small creature would migrate back to the ocean to reproduce, so it may breed at the river’s bottom, where denser marine waters penetrate at high tide.  It is theorized that this unusual mollusk may be in the process of evolving from a marine to a purely freshwater creature.

Olive Nerites in the Aquarium

Another point to recommend the olive nerite is the fact that it feeds only upon the brown and green algae that often coats plant leaves, rocks and aquarium glass, and leaves living plants untouched.  When algae populations decline, its appetite can be easily satisfied with algae wafers  and Spirulina discs.

The attractive shell of marble-sized olive nerite is often colonized by tiny barnacles, adding to its interesting appearance.  They are as resilient to environmental conditions as they are to habitat changes, doing well at temperatures ranging from the upper 40’s to the upper 90’s (F) and in waters of 6.3-8.4 in pH.

Related Snails

Two purely marine relatives of the olive nerite, Neritina  funiculata and Vittina luteofasciata, are sometimes offered for sale as well.  They have wider appetites than their more popular cousin, but do best in marine aquariums that support red and brown algae.

Further Reading

Detailed information and a key to the snails of Florida has been posted by the Florida Museum of Natural History at http://www.flmnh.ufl.edu/malacology/fl-snail/snails1.htm.

Please write in with your questions and comments.  Thanks, until next time, Frank Indiviglio.

Image Neritina reclivata is of a related species, referenced from Wikipedia and originally posted by ictheostega.

Patty here,

There are many snail species available for the marine aquarium hobby, and many of them are beneficial to the aquarium as they perform specific duties aiding in the health and up-keep of the tank. Popular types include ceriths and nassarius, great for sand bed stirring and clean-up, and various Turbo species and other algae eaters like astreas and trochus. For the most part, the majority of the snails you find in shops are there for your aquarium’s benefit. There are also many types of snails for sale that may not be a benefit such as predatory snails, and yet others that may find their way into your reef by hitchhiking on or in live rock or corals that you introduce. I want to introduce some naughty snails, and some really naughty snails you can watch out for to avoid potential issues they may present.

Murex Snails
There are several species of Murex snails that may hitch on rock or collected specimens. Most murex snails are characterized by rough spines or knobs on the shell. They are shaped more like conchs, but are usually rather stout. These are predator snails, and will prey on clams and other bivalves, starfish, and other snails. Some species drill through the shells of their victim to eat the flesh inside the shell. Better safe than sorry with murex snails, remove them to an iso tank or species tank if you want to watch them, they will feed on meaty frozen tidbits if live prey is unavailable.
Tulip Snails, Fasciolaria sp.
Tulip Snails are beautiful creatures, with stunningly banded, smooth shells and a deep pink or red body. These snails are unfortunately carnivores, so they cannot be kept with beneficial snails like turbos and astreas unless you want them to be eaten. They will also prey on bivalves, so no clams, scallops, oysters, or fun little mussles will be around for long if you introduce one of these to your reef either. Tulips are nonetheless offered periodically for sale. They can be kept in the right tank, and are enormously entertaining, but consider their diet before purchasing one. They will feed on bits of frozen mussel, clam, and other meaty foods in the absence of live prey, and can get along with fish and crustaceans that can move away from them.
Flamingo Tongue, Cyphoma sp.
Though these little snails are very pretty, they are not reef safe as they feed only on gorgonians. If you find that one has hitch-hiked on a new specimen, which is not necessarily uncommon, it should be removed from your main reef. They are beautiful specimens, however, for a small species tank. If you have large gorgonian colonies, small pieces can be clipped and place into the species tank to feed the snail.
Black Limpets, Scutus unguis
Most limpet snails are safe and even beneficial in reef aquaria. The Black Limpet will eat algae but also has a tendency to feed on coral tissue, so if seen in a reef, it should be promptly removed before it is able to proliferate. This is a very cool snail, its delicate black mantle may appear to you to be a sea slug, but its white shell is cloaked by the ebony mantel. If you should come across one in your reef, the first challenge is to dislodge it from the rock, which is not an easy task. You may need to remove the rock itself, which may be placed in a small species tank for observation and enjoyment.
Sundial Snails, Helicanthus variegatus
Sundial snails are small button-shaped snails, kind of flat, with a spiraling, checkered shell. The operculum is shaped like a cone. These snails are most commonly seen on Zoanthid polyps, their primary food source. Obviously, these snails can be detrimental to polyp colonies and they should be removed from your reef if you come across them. They hide well amongst polyps and rock, so be sure to keep an eye out, especially when introducing new colonies.
Conchs and Cowries
Just an additional note, there are lots of different cowries and conchs offered in the trade today, and they are some of the most interesting snails you can find. Be responsible as aquarists, and be sure to find out about any species you’re interested in before purchasing them. Most species are safe and functional, but others with size and diet in mind may only be appropriate for large, non-reef homes. Some Cowries can grow to 4 inches or so, and though reef safe, they can easily topple rock and corals in their travels. The Egg Cowry only dines on soft corals. As for Conchs, most offered are marvelous sand sifters like our burrowing conch, but many conchs can grow to be very large and thus disruptive in smaller tanks and tanks with limited sand bed area. Crown conchs, Queen conchs, and many others are omnivores and may prey on bivalves if algae and other foodstuffs are scarce, so be aware of the needs of the snail you purchase.

Until next blog,

Patty