Off topic but for those reading this thread, 400 lbs is not enough weight to cause concern. A 300g tank is closer to 4000 lbs, if not more after all said and done.
my new home build has the fish room floor built with double joists, as specked by my architect. on top of that is a 3/4 ply floor, than a 1/4 base for the wood look vinyl floor. looks great, and spills are no worry
Yeah these guys are right...I have a 210gal Saltwater tank and recently added a 125g Freshwater tank and BOTH went downstairs in the Basement man cave. No way would try it on the 1st floor without having an engineer take a look and likely adding some structural integrity to the floor. Otherwise you're liable to come home one day and find your tank on the floor...the lower one with a big expensive repair on your hands! Good luck.