how close to a water source?

I'd give it about 2 weeks - aquariums put out a lot of humidity and I don't think that tv's can take it -

we have a 20 gallon and 3 - 10 gallon -- we add water about every other or every third day - it even helps to keep moisture in the house -

I'm no expert on water damage to HDTVs, but I'd keep the TV at least a foot away from the filter/pump and you might want to allow a bit more to provide a margin for splashing when cleaning or adding water to the tank. But generally I don't see much of a risk.

That said, I'd want to be sure the TV is on a good stand just in case the tank broke just so the water couldn't get in the TV.

EDIT EDIT

If the humidity level is high enough to hurt the TV it's too high for the building and will cause windows to ice over and the structure to rot. Humidifiers in winter put out gallons/day so I still don't see an aquarium as a problem as long as water doesn't directly get on it (and even then a little bit won't hurt)

That said, why does the landlord get to put his aquarium up against your TV ... or are you only renting a room? If so, and you are worried put the TV in your room.