Re:snails and seahorses

Dear Tammy:

Yes, that’s good thinking, Tammy – any snail that develops a habit of crawling on the ponies should be removed and relocated to another tank. It’s possible that the snail in question was only interested in the algae that often grows on seahorses, particularly their heads and necks and dorsal surfaces, which are closest to the light source, but that still poses a risk to the seahorse nonetheless. Snails have a rasp like organ known as the radula that they use to scrape algae off of hard surfaces, in the case of herbivorous snails, or to rasp pieces of flesh from a carcass or meaty meal, in the case of carnivorous snails.

In either case, whether it’s a herbivore carnivore, a snail that clings to your seahorse and begins rasping away with its radula can easily penetrate the skin and even the exoskeleton of the seahorse, so it is always best to remove a snail that prefers to forage on the seahorses rather than the live rock and substrate of the tank.

The Margarita snails are not a good choice as aquarium janitors for a tank with tropical seahorses, Tammy, because they are adapted to cold water and will eventually weaken and die when kept in a warm water tank.

This is what I usually advise home hobbyists regarding selecting a suitable cleanup crew for a seahorse tank, Tammy:

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No matter what you call them – aquarium janitors, tank cleaners, sanitation engineers, marine maintenance men, or simply scavengers – these are the good guys, the beneficial invertebrates that we deliberately introduce to our aquariums to serve as the cleanup crew. Make no mistake about it, they are as indispensable for your seahorse setup as any other tank, perhaps more so. They perform a vital role in the aquarium by keeping the undesirable nuisance algae under control (including diatoms, hair algae, and red slime "algae" or cyanobacteria), by aerating and turning over the sand bed to keep it clean and healthy, and by helping to maintain optimal water quality by cleaning up detritus and scavenging uneaten leftovers and other organic wastes.

Assorted snails and micro hermit crabs form the backbone of the cleanup crew in most seahorse tanks, but the proportion of snails to hermits is a matter of personal preference. Many hobbyists favor using nothing but a variety of snails, others favor a 50/50 mix of snails and hermits, while others like to use a preponderance of snails with just a few hermits. Personally, I prefer a cleanup crew consisting of a mixture of assorted snails and micro hermits (heavy on the snails but very light on hermits) at a density of no more than 1-2 janitors per gallon at the very most. But if you are new to seahorse keeping, the safest plan may be to go with aquarium janitors that are 100% snails of various types, which will eliminate any possible mischief the hermit crabs may otherwise get into from the equation.

A varied assortment of snails is very desirable because different types of snails have different habits, seek out various microhabitats within the aquarium, and prefer to eat different things. Some are herbivores that feed on microalgae, and some of the herbivorous snails prefer to graze on it from the substrate, others like to clean it from the rocks, and still others love to scrape algae off the aquarium glass. Furthermore, the different herbivorous snails tend to specialize on different types of microalgae and have definite preferences as to the types of algae they eat, so it’s important to have a nice variety of snails that cover all the bases in that regard. Including too many herbivorous snails of one kind can mean that they will quickly devour all of the alga that is on their particular menu, and then face starvation, while other types of algae go unchecked. Along with the vegetarians, it’s equally important to include some omnivorous snails in your assortment, which will go after meaty leftovers. And you’ll want to have plenty of detritivores, too, which will feed on detritus and scavenged decaying organic matter in the aquarium.

The desirable snails can thus be divided into two broad categories – herbivorous snails or grazers, which are the algae eaters, and the omnivorous/carnivorous snails that will take care of meaty foods. The latter are scavengers that are attracted by the orders of death and decay.

The herbivorous snails include Trochus snails, Astrea and Cerith snails, Nerites, red foot moon snails, Stomatellas, Collonista snails, and, of course, the ubiquitous Turbo snails. As a rough guideline, and appropriate stocking density for these herbivorous snails in a seahorse tank is approximately one snail per gallon (with the exceptions of the Turbos, which are only suitable for larger aquariums and should be limited to no more than one specimen for 20-30 gallons). Try to distribute the appropriate number of snails for your particular tank fairly evenly between the smaller Astrea, Nerites, and Cerith snails, and then finish up by adding a few of the larger Trochus and red foot moon snails to make sure that your snail assortment will be able to handle all forms of algae that may appear in your aquarium.

Okay, now that we have discussed some of the most common herbivorous or grazing snails that are desirable aquarium janitors, it’s time to move on to the snails that don’t like their veggies but that will aggressively cleanup the meatier leftovers in the aquarium. Omnivorous/carnivorous snails for the aquarium are indispensable for grazing on detritus and cleaning up uneaten frozen Mysis in the seahorse tank, and consist primarily of Nassarius snails and Bumblebee Snails, both of which are readily available.

Nassarius Snails

Nassarius snails are terrific detritivores and amazingly active for snails. They’ll bury themselves until they detect the scent of something edible, and then erupt from the sand and charge out to clean it up. They do a good job of cleaning up meatier leftovers such as uneaten Mysis and can fill the role played by microhermit crabs for hobbyists who prefer a cleanup crew consisting only of snails.

There are several species of Nassarius snails, some of which are bigger and others which are relatively small. They all like to burrow and conceal themselves beneath the sand, so they are seldom seen until feeding time for the seahorses, whereupon the scent of the frozen Mysis will bring them running. For this reason, it is best to stock the Nassarius snails relatively sparingly compared to herbivorous snails. A stocking density of perhaps one Nassarius per 5 gallons is about right, since too many Nassarius may result in them swarming the feeding station and becoming a nuisance at mealtime, rather than restricting themselves to leftovers (Renée Coles-Hix, "Choosing Common Cleanup Crew Critters"). Every seahorse tank should have its share of Nassarius snails to tend to uneaten Mysis before it has a chance to begin to decay and degrade your water quality.

Bumblebee Snails

Bumblebee snails are also meat eaters and were often used in place of Nassarius snails before the latter became readily available to aquarists. As their common name suggests, their shells are brightly colored with contrasting stripes of yellow and black, which makes them popular scavengers with marine aquarists.

Nowadays, however, Nassarius snails are vastly preferred because the bumblebee snails are actually members of the whelk family, and are predatory in nature. That means that they are not content to scavenge in the aquarium, and will actively predate snails and worms (Renée Coles-Hix, "Choosing Common Cleanup Crew Critters"). Naturally, that spells trouble if the bulk of your cleaning crew consists of small herbivorous snails that the bumblebees regard as prey. They will also deplete the number of beneficial critters in your sand bed in the process. Bumblebee snails may have to place in a cleanup crew that consist primarily of hermit crabs, but must be excluded from a cleanup crew that consists of assorted herbivorous snails. The bumblebee snails are especially dangerous when introduced to a newly established aquarium, where the lack of suitable food means that they will turn their attention toward the other snails in your cleanup crew.

The hobbyist must also avoid other predatory snails such as tulip snails, whelks, horse conchs, crown snails (Melanogena corona), and the venomous cone snails (Conus spp.), which can kill a human with a single sting from their harpoon-like radula. Cone shells have a venom that is far more potent than that of even the most poisonous snakes. Tulip snails, horse conchs, whelks, and crown conchs will hunt down and eat the other snails in your cleanup crew, whereas cone snails prey on small fishes in addition to presenting a deadly hazard to the aquarist.

To sum up our discussion of snails for your cleanup crew, let’s review a quick compilation of the desirable snails to include and the undesirable snails to exclude when you are assembling your sanitation engineers.

Desirable Snails to Include:

Nassarius Snails
Astraea Snails
Trochus Snails
Nerites
Cerith Snails
Red Foot Moon Snails
Turbo Snails – as needed
Fighting Conchs (Strombus sp.) – as needed

Predatory Snails to Avoid:

Bumblebee Snails
Tulip Snails
Whelks (in general)
Horse Conchs
Crown Snails (Melongena corona)
Margarita Snails (will gradually weaken and die from heat stress when kept in tropical tanks).
Cone Snails (beautiful but deadly!)
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Okay, that’s a quick summary of some of the more desirable snails to include in your arsenal of aquarium janitors, Tammy, and some of the undesirable snails that you should avoid for your seahorse setup, Margarita snails fall in the latter category and you should remove them from your seahorse tank, particularly if they are taking an unhealthy interest in the ponies.

Best wishes with all your fishes, Tammy!

Respectfully,
Pete Giwojna, Ocean Rider Tech Support