Again thanks for all the input. As previously stated the tanks are not an issue with the landlord.
I wasn't aware we were talking about a 300g+ tank. I guess I just assumed making sure it's okay with your apartment complex or at least checking your lease is common sense for a grown adult. I have some form of concrete floor I believe and I would never dare more than my 125g.There's a reason several people have mentioned that he should clear having 300+ gallons of aquariums with the landlord...it can be a real issue. One of the things I like best about this site is people sharing ideas that I may not have considered. If he doesn't want to hear it, he can ignore it. But why not ask the landlord about it and find out now if it will be an issue as opposed to having the landlord freak out when they come to service his A/C unit, fix a leaky toilet or any other issue?
It would be foolish to rely on what some random person on the internet says about a floors ability to hold a load when the specs of the floor have not even been laid out. There is a difference between a couch holding a few guys for a few hours a day (transient load) versus tanks that have the flooring under a longer term (24/7) live load.
The last place I lived had concrete floors and I would have been comfortable setting up a 240G on it (I was on the 7th floor). My brother owns an apartment building with wood floor joists that was built around the same time as my old apartment with concrete floors and a 50G would cause his floors to sag. Both buildings were built to code for the type of construction used at the time, but there are drastic differences in how much weight each can hold.
To the OP, if you are going to keep the tanks a secret, and you aren't able to find a unit on the 1st floor on concrete slab foundation, the least you should do is find out which way your floor joists run and set your tanks up perpindicular to them. The more floor joists your tank sits over, the better. Placing the tanks near a load bearing wall would also be a good idea. And lastly, I wouldn't multi-task when doing water changes. Losing track of time when you are filling up a tank could spell disaster/financial ruin for you. I know you didn't specifically ask for that advice (sorry Jon M), but I'll still offer it up.
Best of luck.
Yeah that person turns out to be a civil engineering student, structural being the focus, and would usually be a good authority on structural questions, but it would be hard to tell without the blueprints for the building and knowing the materials used to build the apartment, but usually it is a bad idea to put so much weight in a concentrated areaJust like any other information provided by members of this site, I would take it with a grain of salt. I'm sure you realize that the person saying you will be ok placing that much weight on the 4th floor of an apt building could very well be an 11 year old kid from South Cackalacky...hardly an authority on the load bearing capability of a structure.
Yeah that person turns out to be a civil engineering student, structural being the focus, and would usually be a good authority on structural questions, but it would be hard to tell without the blueprints for the building and knowing the materials used to build the apartment, but usually it is a bad idea to put so much weight in a concentrated area