I have a 14g bio cube and I pulled the lid and made it rimless. Making it rimless was fairly easy and looks great. I also cut down the first baffle in the back to lower the water leave a little so when the magnet is move it doesn’t splash as much if any water out.
I left the rim on mine. Cut some eggcrate to size to keep the fishies in and built a light stand from 3/8"x 1/2" aluminum u-tube from HD, drilled/tapped the aluminum and used nylon bolts to hold it all together, then painted it black. Not the most elegant, but the wife wouldn't let me hang the light. ;Blackeye