Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
That little bit out of level is not usually a problem.
Ditto Bruce: Shims should go under the stand, make the stand as level as possible. Level bubble touching the line is pretty close! Most of mine are about like that. None are farther out of level than that. Yes, adding water can alter the level. If it goes out of the tolerance range (level bubble within the lines) then drain and re-level.
Tank sits flat on the stand, perhaps with a thin cushion. I use Styrofoam sold for insulation, but I think that is kinda thick. No shims under the tank itself.