I built a stand for a 135 based on structural plans from garf.org. I made changes to the design because my tank sits 58 inches off the ground and I didn't think their calculator was safe for this elevation. I added 2x4s under each corner and sheathed the stand with 3/8 ply on 3 sides. used 3/4 ply top and bottom and bolted it to the wall. You won't need the additional structural support for a 55.