One corner of rimmed cube not flush

I purchased a 35 gallon seapora cube and stand back in February. The stand it was sold with I believe was made for the JBL cube style aquarium's as the front wasnt square and had rounded corners. So when set up only the back two corners were flush. The front two corners were slightly exposed due to the rounded front of the top panel. The cube is a perfect 20x20 aquarium so approximately 35 gallons. My main issues with the set up was the swaying of the stand when set up. It would sway from left to right with a slight nudge. Having 3 young children I become stressed after awhile and decided to try my hand at a DIY stand. It's made out of 2x4s with the standard design. Top frame and bottom frame with 4 guides and supports on each side of the guides between the upper and bottom frame. This is built like a brick and I went overboard doing so. It has approx 100 2.5 deck screws holding it together at the joints combined. Stand has 2 back supports running horizontal as well just for extra precautions from swaying as I wanted the height at 32 inches. Front has a door made out of left over 2x4s. Left, right, and back sides were left open so I could easily access canister. My concern is that after having this set up for two months, on my last water change I noticed the back left corner has a gap between the black rim of the tank and stand top frame. I made sure it was flush during the build using a level. I would guess the level is off as that's the only explanation for this flaw. All other 3 corners make direct contact as well as the rest of the trim. Just the back left corner which sits 5/8 off top frame connection. I've attached pictures showing this. The gap isnt much either. Cant really measure it but its wide enough to firmly squeeze 4 cards between. I never fill it to the top for flow reasons so it stays approx 2 inches from top and with a 2 inch substrate level I would guess its holding 30 gallons of water. Should i be concerned? I've read all 4 corners of these rimmed tanks need supported. But I'm also thinking back on how it was sold with the original stand and how the front two corners were exposed slightly when set up. Am I being over paranoid? I really dont want to spend a whole day rebuilding and painting a new stand just to find out it could potentially be a flaw in the trim or that one 2x4. Using a new level it appears to be perfect when checking top and bottom frames from the sides.

 

Try shimming the stand at floor level, directly under the problem area. Maybe that will push the stand up to meet the corner. As a last resort, shim the corner gap between the stand & tank.
All corners need to be supported as to avoid twisting. The resulting torque can eventually crack the glass.

 

Thanks for your response! As for shimming I tried using wood shims and it didnt work which is why I think either the trim or that side 2x4 is flawed/off. I've been thinking of shimming that gap between the tank and stand. I've read everywhere not to tho. Would I do so with one of the wood shims? Cardboard?

 

Thanks for your response! As for shimming I tried using wood shims and it didnt work which is why I think either the trim or that side 2x4 is flawed/off. I've been thinking of shimming that gap between the tank and stand. I've read everywhere not to tho. Would I do so with one of the wood shims? Cardboard?

I‘d suggest using composite shims.

 

How feasible would it be if I were to either A. Add 2x4 braces running across horizontally on the very top. So two pieces. One in the front and back. I could then use putty to fill that slight gap and then paint over for cosmetic. Because the back sits completely flush minus that one corner this theoretically would have all four corners supported and solve the problem. Or B. Replace that one side 2x4 support as it's the culprit I believe. After measuring both ends of that piece that back corner is 1/32 of an inch shorter which is where the gap is. If I do this route, I would have to unscrew the 6 screws in each end of that piece. They are 2.5 deck screws. I could then attach replacement piece using 3 inch deck screws. My only fear going this route is will it compromise the integrity of the stand as a whole. Thoughts? Just as an fyi I took prior advice and its shimmed using composites in between stand and rim.

 

The problem might not be with the stand, but with the bottom plastic rim. Sometimes they are applied imperfectly.
IMO, as long as the problem corner is supported by the shim, likely no worries.
If the shim job is ugly, maybe replace w/ a heavy duty rubber exercise mat. Cut to size and place under the tank.
Current wisdom frowns upon shimming between the stand & tank, but your tank is relatively small w/ no long sides. I think shimming in that manner will be fine.

 

Thanks. I realize I'm probably over concerned but with the set up it's pretty expensive and ofcourse being in the kitchen where theres some foot traffic well I've been obsessing since I noticed the gap even tho it's been a while since placed on the diy stand. I'm going to drain after breakfast this morning and try the mat approach to see what I think. I appreciate the help!