Whatever the problem was...
It struck the Ropefish quickly, and unfortunately he did not survive through the next couple hours.
Upsetting, these guys are expensive for me and it is very rare to find one in the pet stores around me. I got lucky finding the two I have (had, one now) as I was not even looking for them but had always wanted some, and just found a few for sale at a local shop when I wasn't even looking for them at the time. They ran me about $25 a piece and were just a little over 6 inches long at the time.
The one who died, had grown to at least 11 inches! He's the one in my Av pic.
Now I'm going to be concerned for the other one for a while...