Last Updated: 4/12/12
Aquatic Snail Information
A pond is not complete without aquatic snails. Many people add them in aquariums as well. If you set out to create a snail-free pond, they will always mysteriously show up. Whether they survived a chemical dip on plants or took a ride on a bird's legs to get there, if you build it, they will come. Aquatic snails are the clean-up crew for the pond. Most of them will eat surface algae, small pieces of plants, dead animals, and leftover foods. Some of them will damage plants. Most of them will only improve the overall health of the pond. Snails, along with tadpoles, are often added to eat pond algae. It is rare for snails to overpopulate a pond as they do in aquariums. This may be due to the larger number of natural predators present and other natural factors.
Snails belong to Gastropoda. They have a single, coiled shell. A pair of sensory tentacles come off their head with eyes at the end. Their mouth has a rasping tongue, called the radula, to shred food. Most eat plants (including algae) but some eat dead animals. Parasitic worms may live in them. Snails move by a muscular, slimy foot under their body. Algae naturally grows on most aquatic snails. It provides some camouflage.
Information on pond snails is sorely lacking on the internet and in books. The pond snails are bad enough; the land snail information is basically non-existent! I have not included any information on land snails as I know very little.
Most snails are hermaphrodites. This means that they are both male and female. All hermaphroditic snails can lay eggs. They can "mate" with themselves and thus only one can reproduce in an aquarium or pond. They also breed sexually as often as possible. Most snails lay eggs but some, like the trapdoor snail, give live birth. Trapdoor snails and a few other species of snails (such as apple snails) are not hermaphrodites. They can only reproduce sexually.
Underwater Snail Eggs:
For those snails that lay eggs in the water, snail eggs look like little jely blobs stuck on hard surfaces and plants. Favorite places to lay eggs include aquarium glass, clay pots, bricks, large plant leaves, and almost anywhere sturdy enough. The eggs begin clear but soon get a dark spot which grows larger as the snails grow. Unlike fish eggs, you will not see two large eyes looking up to you. After about 3-6 weeks depending on species and temperature, the babies emerge. They are quite vulnerable to being eaten at that time. There is nothing special to be done for their care aside from providing foods their parents like if algae and plants are scarce. People often add snail eggs to aquarium and ponds without knowing it as the eggs come hitching rides on live plants or even inert materials moved from another aquarium or pond. Rarely, eggs may be infertile or die. In that case, they will turn white as fungus attacks them. Healthy snail eggs are clear with a dot inside.
Above Water Snail Eggs:
Apple snails lay eggs above the water line, usually on plants but, in an aquarium, they often lay eggs on the lid. Apple snail eggs are yellow or pink. They need to stay damp but not submerged in order to develop. See the section on apple snails for more information.
There are two types of snails. Gilled snails have gills and can close their bodies into their shells with a plate, or door. Gilled snails usually lay their eggs in jelly-like cocoons above or under water. The trapdoor snail (actually a livebearer) and apple snail are two of these. Pulmonate snails have lungs. They either come to the surface to breathe, or some breathe through their body surface while underwater. They cannot close their bodies into their shells. Pulmonate snails usually lay their eggs in gelatinous masses under water (the Malaysian trumpet snail though is a live-bearer). Examples are pond snails and ramshorn snails.
Snails will usually find enough left over fish food, algae, and live plant material to eat. If you need to supplement their feeding (like in a bare tank), you can feed lettuces like romaine, kale, or cucumber (split, remove seeds, attach to something heavy to sink). Only provide as much as they will eat over a day. Each day, remove uneaten portions. A one inch snail might eat a 3" x 2" piece of romaine once every two days as an example. Snails do not need fresh vegetables daily unless there are a lot of them, or they are large like apple snails. One keeper of apple snails reports that five 4 cm apple snails (P. flagellata and P. glauca) might eat one big lettuce leaf in a night. Snails will also eat the sinking tablets made to feed bottom dwelling fish and plecostomus. There are a number of algae-containing tablets for algae eaters like plecostomus that work well as well as Tabi-Min by Tetra that is a sinking food pellet. The snails I have had will try to eat most any sinking fish foods.
I have been asked a number of times about how to tell if a snail is dead. People buy new snails, and they do not come out of the shell. Sometimes a snail was active and then appears to be holed up in the shell. If a snail is scared due to its new home or has undergone some stress like something trying to eat it, it may hole up in its shell. Water quality problems and temperature extremes may cause the snail to stay holed up as well. Sometimes, it will not come out for a few days. Beyond a few days, it must come out or risk starving. Often, it may hole up during the day and come out to feed at night. If a snail shell is in the same position for more than three days, and the snail's body is not visible, the snail is most likely dead. I give a snail about a week to move before throwing it out in my ponds. In tanks, it is important to remove a dead snail larger than 1/4 inch as it can pollute the tank quickly. You can put the snail in a bucket of water and set it aside with some food and see if it moves over a few more days. Taking the snail out and smelling it will help to decide. A dead snail smells REALLY bad, like a rotten egg! If the snail is in a different place each day but you never see it out moving, it is coming out at night. Surprise it after it is dark with a flashlight or room lights to see what it is doing. Some snails only come out at night. Apple snails are known to sometimes go somewhat dormant and float or lay on the bottom for days or even weeks. The reason is not known. Snails in ponds will go somewhat dormant when the temperature goes below about 50 degrees F and may stay in one place for a long time.
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