Haven't used those but a razor blade and a bit of elbow grease go a long way with no risk of chemical contamination if you aren't going to move the fish out first. You just have to keep the area wet and mind your angle and seams so you don't scratch the glass or cause a leak. A lot of people end up etching their glass permanently simply by going at it with too abrasive a scrubber. I know those green pads are trouble, can't say on the Mr. Clean.I need to get some more of those Mr. Clean magic erasers, the original kind without any additives, those work good for cleaning off the hard water deposits.