most fish are fine for a month without food. Especially if they are in a planted tank. Just make sure they have all been well fed for several weeks before you go away and don't add any new fish before you go.
You do run the risk of problems occuring tho and if you aren't there to monitor things you could come back to an empty tank, or at least one without fish.
If you could have someone from Uni pop in from time to time to check on them and give you a call if anything looks funny, then you would probably be better off.