I had a nass snail get sucked into the return pump, it was quite gross and sad. It was on the glass infront of the pump intake and stupid me, i decided to move the pump back a bit, instead of turning it off first, and the suction killed the snail
on the other hand, my clown goby went overflow surfing and eventually ended up in the return section. this time i was quick enough to turn off the pump first! lol those gobies can sure jump high and move fast!