so the tank i was surprised with is a 42/36/12 with a 30 gallon sump. Do you think it should spread over a wide enough area?
You are looking at an 80 plus 30, equals 110, almost 1000 pounds in just water, tank and stand weight,
Your footprint is 10.5 square feet.
By standard dispersion of weight for a traditional 2nd floor sure floor, you are looking g at over 70lbs per square foot above traditional allowqnces.
Now, if you put it directly over a joist, or better yet, put it on top of a set of beams that are balancee on the floor joists, you can mitigate it some.
Realistically, I have seen much, ,uch heavier tanks go onto second floor apartments, so I would not worry too much about it.
But I would test it for at least a week half full, then another week 3/4 and see if the floor adjusts at all.
You should be fine, but I have been in your shoes, living in a an apartment that felt like I was going to fall through the ceiling into the people's home below on several occasiins.