I removed the rim from a bio-cube 29 while it was set. Very easy with no concerns regarding structural integrity. Started with a small hacksaw blade and cut the rim just outside of the rear chamber on both sides, careful so as not to scratch the glass. Then slide a Razor blade, the more substantial ones up the sides of the rim in order to cut the silicone seal. You will still have to "muscle" the rim off but once you get one side free it allows leverage to continue around. Then using fresh blades you can clean the black silicone off the glass. That can be a little time consuming to get it right The tank was lite with a 150MH rim mounted light. I thought it looked better rimless. Good luck. Ray