I had a few small blind cave tetras in a newly set up cave biotope tank, and the filter I had bout didn't come with a grate to cover the intake (thank you That Fish Place
).
The next morning I found one of the BCTs that had been sucked into the filter intake tube and minced by the impeller.
There were pieces of the poor little guy all over the tank.
Needless to say that I now ALWAYS put some kind of grate over all my filter intakes
.