U would be amazed at how much weight your floors will hold. A 30 gal tank isn't gonna weight more than 400 lbs with water, rock, equipment, sump, etc. I say go for it!!
Lol no hes a Architect and head super at a construction company. Been construction his whole life. I believe him when he says anything about it. Its not biggie. If i score this job we will be moving soon