Whelk?

[Frogger]

They are nocturnal. They are hard to find during the day at night they are everywhere.

Biggest issue with them is they get stuck in my gyre's and damage the blades. I have to make sure I have the fine mess filter on my gyres to keep them out.

They go over the overflow and also get stuck in the ball valve. I have to open it up fully once a week to clean out the ball valve