I was really nervous when i was getting into larger tanks. From what I've gathered though, generally a 125 gallon tank is safe for most houses on the first floor. I didnt really worry about the tank bursting, i was worried about the floor collapsing from all the weight and all the expensive damages that would happen.
For a good two months or so i was paranoid about any creaking sound I may have heard or thought i'd hear. I would keep checking the wall mouldings to see there were any gap increases indicating the floor was sagging from the weight. Anytime I would spill/flood water, i would be even more paranoid if the water was weakening the floors further.
For my own piece of mind, i probably wouldnt go more than 150 gallon, not even a wider footprint 180 without reinforcing my floors. If the floor ever did collapse, the house damage along with the broken tank and dead fish/plants, I surely would instantly be out of the hobby (my choice or not

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