"RubenD" wrote in message . net...
I don't know about crabs catching fish, but I've seen them fighting each
other. They grab each other the whole day and then I would find the pieces
of one laying on the sand. I'm talking about red leg hermits. I guess
there is always one bully in the group. Most of them are very peaceful.

Red leg hermits called "scarlet hermits"? The small ones?
I have 4 of them and I do not see any interesting fights...

Maybe you observed mating behavior just after crab molting?
And that would be the reason for pieces of old red skeleton laying
on the substrate. Crabs/shrimps mate just after molting because
they need soft bodies for the mating act, so the molting gives
a perfect opportunity for mating.

Now, if you talk about my coral banded shrimp, he chase my fish, even try
to get them with his claws, sometimes with some success. Still, I haven't
seen any fatalities.

I have never had this kind of shrimp.
It was always too scray-looking for me to add it to my tank :-)