As a test (as I was cautious even after the shop keeper said it's fine), I bought 3 Amano shrimp to add to my aquarium. One day later only one was still there (right top of the pic). All three were too large to get into the filter (except through the output), so I guess they were eaten.
Aside from the fish in the photo, there are two antenna catfish and two loaches (the variety that is only on the ground and their mouths are too small to even eat the fire tetra).
As I watched the single survivor today I found him hiding only in the almost out of water corner of the filter system. So I guess he must be deathly afraid.
Now what I'm asking is, is there anything wrong with shrimp of that size and this aquarium? Or do I need more shrimp-specific hiding places, or is there a deathly threat to them that I don't recognize as such? (Currently I'm out of ideas as to why the other two died and that one seems afraid, and the shop keeper wasn't a real help there either.)
