Worms, crabs ... ?
Think I got one crab in there.
Cos found its molted shell twice.
But no casualties some far, so no rush to catch the rascal yet.
Anyway, it'll help to clean my tank - those uneaten food.
When I had this tank in my office (before I brought it home), think I caught close to 10 crabs in there. 2~3 are big ones. Those time, I had missing fishes now and then.
Caught a few worms, big ones, and threw them away. But left the small ones behind. Cos good for your tank's eco-system.