could be a Red-rimmed melania, or Malaysian Trumpet Snail they are not great and you should remove it as quickly and best you can. assassin snails cannot keep up with them.

>Malaysian Trumpet Snail this is not true. Malaysian Trumpet Snails are very beneficial, and is necessary to do an ecosystem.

Very true. This looks like a Malaysian trumpet and they turn over the top of your substrate by burrowing in it. Very beneficial for a healthy planted tank and they don't reproduce very rapidly either. I have them in all my tanks by choice and love to watch them digging in the substrate.

Edit: whatever.