I made sure to make my tank perfectly level. took some time but i think it is well worth it, i dont like seeing the water level change from one end to the other
what about on carpet. i keep reading that carpet should eventually level the tank out.. my tank has been sitting on carpet for a about year now and its still just as uneven. which i guess is a good thing.
maybe ill just drain half of it and try to put some shims under one side.
As long as the floor is flat the water depth will never be greater than the maximum depth when the tank is perfectly level so it shouldn't be an issue as there is more pressure on any particular side of the aquarium when the tank is full and level than at any angle. If the floor isn't flat it can result in warping of the stand and pressure points in the tank.
the less level a tank is the less water there is, the less average depth, the less maximum depth, the less pressure on each panel, the less pressure on every point on the panels and seams.
Obviously an extreme example of angle but based on a 24x24x48 120g tank at 45* holds 60 gallons of water. Angled front to back for these numbers.
The maximum water depth drops from 24" to 17", average water depth on the portions of the panels that are touching the water drops from 12" to 6".
Average pressure on the portion of the panels touching water drops from 0.43psi to 0.22 psi, maximum pressure drops from 0.87psi to 0.61 psi.
Maximum force on the panels drops from 495 lbs each on front and back and 248lbs per side to 253 lbs front and back(bottom) and 62lbs per side.
I keep mine as level as possible just out of personal preference.