Eupterus;5017647; said:
That is a very common misconception that is simply not true...
　
It is important that the tank sit "flat" on the stand, but it doesn't matter one bit if the tank is "level"...
　
If the tank does not sit flat to the stand then the glass panes can torque and crack under pressure. It is highly unlikely, but possible, for the torque to not be enough to crack the glass but over time be enough to slit the seams.
　
To ensure the tank sits "flat" on the stand, set the empty tank on the stand and see if it rocks.
　
Being "level" is not structurally important at all, but most people want the tank to be level for aesthetic purposes. To see if the tank is level put it in place and fill water up to the bottom trim. The water will rest completely level, then compare the top of the trim to water's surface to see if it's level.
　
If the tank does not trim, then fill it to a given water depth, such as 1", then compare the four corners to ensure water depth is consistent.
