The answer to you question depends on the length of span, size of joists and if there is any load bearing partitions with the range of the span. Need more info.

Shanek, this is definately something you should have a professional look at as your tank exceeds the live load that is required for the floor of your apartment.  Code (IBC and UBC) specifies that the engineer check for 40 PSF, and your tank is on the order of 160 PSF.

Your best case scenario is to put it directly over load-bearing walls, but that doesn't guarantee the landlord will go along with it and it doesn't guarantee the current condition (termites, perhaps) of the building is capable of it.

swBausch is right.  Check with your landlord before doing anything.  Yes your load approaches 150-160 psf but that would not be applied over the entire floor as would the 40 psf design live load.  Still, a 1000-1200 lb point load is pretty heavy.  If your land lord allows this, I would do as swBausch says, put it over a load bearing wall or column if you have one, and it would probably be a good idea to hire a professional to take a look at it.  If something goes wrong and the aquarium causes damage, do you want to be responsible?

I suspect you will be required to obtain renter's insurance for this. It is standard practice for most apartment complexes for aquariums and waterbeds. On the plus side, renter's insurance is cheap and it also protects you against many other civil liabilities.