180 gallon on the main floor

[Aquattro]

That's an absolute maybe. Or not. Depends on floor material, what is under it, load bearing wall, middle of room, etc

[FishyFishy!]

You'll be fine. Just make sure that it sits accross the joists, not parallel with them.

Mine is main floor, and there was zero deflection.

Mine is here above:

[mihaivapler]

As long as the tank run across the joists and will be close to the wall where the joists can carry a bigger load you are fine,I have a 130 plus 30 gallon sump for a year now and the floor doesn't show any signs of stress.just go with a longer tank so you are spreading the load over as many joists you can..my tank is 6 foot and seats over 4 joists

[riceboy]

Thanks for the tip guys.