<a href=showthread.php?s=&postid=14802845#post14802845 target=_blank>Originally posted</a> by chris4869
You can try flipping the tank on its side, and use enough undiluted vinegar (a couple of millimeters) to cover and soak the entire surface. You just need to soak it for an hour or so, and use the a razor blade trick to clean the glass. Repeat for the other 4 walls. You'll use less than a gallon of vinegar at full strength for this project.