Leveling a Tank

[Enigma]

I can fit a piece of paper between the trim and the stand on the front over a length of around 6". I missed that earlier. I checked that the centre of the tank was in contact with the stand. The gap is to the left of centre.

I've got around 15 gallons in the tank so far. Is it important enought that I should drain it and use the foam?

If so, could I use layers of laminate flooring underlay? We've got piles of scraps of that (Hubby installs wood floors for a living).