I had a similar thing happen, although not with the salt...I had just set up my 55 gal
and had transferred some plants from my 30 gal
. The next day I found 4 baby fish in the 55 gal
! Until they grew a little I didn't know what fish they had come from but they turned out to be rainbows. Unfortunately I couldn't catch the little guys (try catching a really fast speck in a heavily planted 55) and when I started adding other fish...well, you can guess what happened.
Good luck with the little guy! He's one tough fish!