One of my golden barbs (the biggest, fattest one of course!) got itself stuck in a castle I had in my tank a few months ago. I only found him when I went into my dining room to put something away and there he was, wriggling like mad with his tail sticking through one way and his head sticking through the other.
At first I panicked, because I'd never had this sort of thing happen before.
I managed to help him out luckily, but he looked in a bad way - he'd lost some scales either side of his body, was bleeding and had lost alot of his lovely golden colour.
A couple of weeks later, though, you'd never had known he'd been in an accident. I treated the tank with the appropriate medication, and lo and behold he has made a full recovery. The only evidence is a slight mark on one of his sides, but that's it.
Needless to say he is now back in full fettle, eating anything and everything that I care to put in the tank.
And of course the castle went straight in the bin after that.
I did think "silly fish" when I'd got him out, but was so relieved when he started to show signs of recovery.