eaten

I have 1 balloon molly, 7 harlequin rasbora, 7 neon tetra, 1 swordtail & 1 assorted male fancy guppy (~ 1.5") in my 36-gal tank. My friend recently moved out and gave me 2 relatively big ghost shrimps (> 1 yr old) & 1 zebra danio (~ 1.5"). Strange enough the very next day, my guppy gone missing...

I suspect that my Betta might have nipped off my snails eyestalks and or/antennas. For a long time my Zebra has been sitting in the corner of my tank, moving maybe 1 inch in any direction over the course of 7 days. He's not dead, if I move him manually and hold him in another area on the glass...