Columnaris or something else?
I just lost an angel over night out of the blue and wanted to see what everyone thought had happened. Its fins were perfectly normal and it was eating yesterday, but somehow over night the angel's tail fin eroded and its dorsal fin shows some erosion/dissection as well. My water parameters are in check, reading 0 - 0 - <5ppm: I did a water change 3 days ago just as a weekly maintenance routine.
I also lost two harlequin rasboras earlier last week, but they didn't have any visible sings of illness. The other 3 angels in the tank are hiding behind the driftwood somewhat, but will come out when food is introduced; the rasboras are swimming around like nothing is going on.
The tank is a 90 gallon setup with ~20 rasboras and 3 angels.