I'm glad you finished it on time, because it's a nice little game. Hmm, maybe not so "little".
Regarding the "Exit", there was a room that said something like: "Exits: North, Exit". When you type EXIT, you don't go anywhere. It's one of the unusual features of Adventuron, where it tries to add exits based on what it found in your match statements. It's not a big deal, so don't worry about it.
Regarding the fish and the secrets, now I have to go and find them all. Fun, fun, fun. :-)