Aquatic snails might love climbing up your aquarium's glass, messing up your plants, and being risk-takers by falling from high places in your tank. But floating might seem a bit abnormal. Floating isn't usually a sign that your snail has passed away, although it might indicate that he's unhappy with the water. Some snails float because of trapped air in their lung, while others eat away at film at the top of the water surface.
When some snails close up -- mystery and apple snails are notorious for this -- a bit of air gets trapped inside. Like a little balloon, they say goodbye to the bottom-dwellers and start floating to the very top of the tank. Once they open up, they'll fall back down to the bottom, or suction onto something. You'll often see this with snails who have a lung.
Take a look at the surface of your water and you might notice a milky film. It most often results from harmless bacteria or poor surface agitation, which allows plant protein and food particles to join together and form a film. Regardless of the reason, the film isn't harmful to your swimming friends. But some snails, such as pond snails and Malaysian trumpet snails, love to munch down on it. They float along the top, upside down, eating away at the film. Sometimes you can see their little mouths moving. Adding an air stone or increasing your filter power can sometimes disrupt the film. You can also lay a paper towel flat on the surface for a second or two to remove it.
Bad Water Quality
If your water quality has taken a turn for the worst, your snails might float in protest. You might also see them try to leave the tank by climbing out of it. They're trying to get the heck out of a bad environment. Your primary concerns are nitrates, nitrites and ammonia. Check your water with test strips or the more accurate liquid tests to see whether those levels are too high. Ammonia and nitrite levels should both read 0 parts per million, and nitrate should be less than 40 parts per million. If those levels are out of whack, change 20 percent of the water each day until they go down, and your snails will stop their floating madness.
Knowing whether your snails are just chilling out at the top of your tank or actually dead calls for a bit of closer inspection. Pick up the snail in question to see whether he's closed inside his shell. If he's tightly shut, he's not dead. If he's hanging out of it and not reacting when you touch him lightly, he's probably either dead or very sick. The only way to know for sure is the smell test. Dead snails smell something horrid, usually within 12 hours of dying.
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