I've always been under the impression that shims should be used at the floor/stand contact points to make up for floor imperfections not really anywhere else.
???? right on, sorry I’m not a carpenter buddy. Have a nice day master fish tank stand maker.Chix had it right in #8. You should have bought another length of 2x4 and cut two more corner supports slightly longer than the two you have in the picture in #10. The new slightly longer corner pieces, when affixed, would have lifted the top frame up the few millimetres you needed to fill that gap perfectly.
Two minutes of a task to do the job properly but instead you've botched it. When it comes to heavy fish tanks and the potential damage they can do i'm afraid comments like "I don't care about the look" or "i'll just roll with it" aren't comments that you usually hear.
MrsE88 had it spot on with her "better safe than sorry" attitude.
???? right on, sorry I’m not a carpenter buddy. Have a nice day master fish tank stand maker.