I did apartment maintenance for awhile and if this inspection is being done by the county, they will not care about the tank. What they are looking for are working smoke detectors, fire extinguishers, properly maintained sprinkler systems, general "cleanliness" of the apartment(that is you aren't storing trash in the apartment or otherwise creating a truly unsanitary condition), and that the apartments are generally safe and well maintained. They are not looking for whether you are in agreement with the lease, just whether the apartments are following county code. So about the only thing you need to do is make sure your smoke detectors work and your extinguisher is charged. If these items are missing or not working, you can get a very large fine. I saw people get fined $1200 for taking down their smoke detectors($150 fine per detector, CO+smoke count as two and therefore $300). So test them now.
However, they may have a maintenance person following them around to let them into apartments and go over what needs to be remedied. But if there is no clause in the lease limiting aquariums you should be fine. Even if there is, maintenance guys usually wont care as long as you haven't been rude to them in the past.