Remember that having a few snails in your aquarium isn't necessarily a bad thing, as they eat and eliminate food that isn't eaten by the fish.
Unlike many other snails, ramshorn snails do not breathe through gills. They have an organ that is referred to as a snail’s lung, which allows them to trap air in their shell and breathe underwater. Because they require air, they will often climb to the surface of the aquarium, or simply float up to refresh their air supply.
It’s very important to avoid any ramshorn snails raised in the wild. It it has been reported that if they are raised in a pond, they may carry parasitic flukes that can affect both humans and fish. If you do decide to add some outdoor snails to your aquarium, they should first be kept in quarantine for a least a month away from any fish. Since the flukes require an intermediary to breed, they should be parasite free after about a month.
Vermetid Snails in the Aquarium – Donya Quick's Website
Assassin Snails in the Aquarium - WetWebMedia
Just like any other force, snails can be used for good and for evil. They have a reputation of rapidly devouring plants, multiplying like crazy and turning a former fish tank into an unsightly mass of creeping grey slime, but this is only the dark side of the snails. When properly managed, snails can actually do a lot of good in your aquarium. If you introduce factors that balance their numbers, they will settle in to their designated ecological niche in your aquarium and carry out the same beneficial work that they do in the wild. Snails can even be entertaining pets themselves and some of them, e.g. the Mystery Snail, look really beautiful. Snails and fish eggs Keeping the water quality up in a breeding aquarium is often of extreme importance and introducing a scavenger will help you with this. The problem with scavenging fish species is however that many of them like to eat fish eggs. Even fish species that normally stick to an herbivore diet can be tempted by the look of tasty fish eggs. Snails are however much less fond of eating healthy fish eggs and are therefore a good choice of scavenger in a breeding aquarium. Snails and water quality The exact diet of a snail depends on size and species, but a majority of the snails are scavengers that will feed on plants (especially decomposing plants), algae and dead animals. Some of them are carnivores that will hunt, but only tiny animals such as gastropods smaller than themselves. An animal that will remove dead animals, algae and decomposing plants from your aquarium sounds like a nice deal, doesn’t it? A reasonable amount of snails will actually help you to keep the water quality up in the aquarium while simultaneously keeping algae growth in check. Snails are highly dedicated cleaners that will get into a lot of nooks and crannies where catfish wouldn’t bother. Even though snails can be a good addition to most aquariums, their numbers must be kept in check. There are also certain species, including the abovementioned Pond snail, that need to be eradicated completely if you keep a planted aquarium. Snails are especially prone to multiply rapidly in hard alkaline water and the aquarist must therefore pay special attention to their numbers in such aquariums. Snails need the minerals to form their shells and too soft and acidic conditions can actually cause the shell to dissolve and leave the snail completely unprotected from predators.