After a day, when I turn on the fish light, I see him rush to the glass. He goes up... and does what is in the picture! He keeps getting farther and farther off of the glass! If he falls he goes back up! I am a first time snail owner, too. I have 6 flame tetras, two bottom feeders, and another apple mystery snail. They are both males (cannot mate). Please help!

  • Keep an eye out for your fishes behavior. Snails climbing up on the glass, repeatedly like yours, or when a lot of snails do it at the same time, is often a sign that the oxygen level in water in getting too low. Make sure the water is frequently partially renewed. However as pointed out, this can be a perfectly normal activity for a snail, but I would be worried if he goes back there all the time even if it falls, if the snail was not doing this before.
    – Manuki
    Jul 9, 2019 at 15:12

2 Answers 2


Two possible things I can think of judging by the pic:

  • Just grabbing some air. Apple snails have a kind of snorkel they use to breath air from the surface. You can see it in the right of your picture.
  • Trying to eat stuff from the water surface. If you look at the water surface from an angle, you might see a thin, somewhat smeary, almost oil-like looking film on the water surface consisting of algae, bacteria, and other microorganisms. The snail tries to eat off that. Smaller snails might even be able to "sail" right under the surface, but adult apple snails are simply too heavy.

Lots of water living snails have both a lung and gills, and the lung takes up oxygen if there is too little oxygen in the water to fully supply the snail with oxygen from the gills.

If you look from above, you will see a small hole opening in your snail where the snail breaches the surface of the water (sometimes the hole is several milimeters big); this is the lung of your snail.

Snails have this backup so they can live in water with very little oxygen.

It is normal behaviour for snails to go to the surface even in well oxygenated water. If there is very little oxygen in the water, they will go to the surface more often.

Snails go to the surface to look for floating food, too.


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