it take a alot of force and 'hardness' to scrath glass. it it is acrylic, that is different, but still most things growing dont even scratch that, and i cant say i have ever heard of sponges scratching, as they are usually very soft.
Originally Posted by mcbdz http:///forum/post/2816436
I be careful with a sponges as stated above, if your just cleaning the tank i would invest in a MagFloat they're fairly cheap and work great
First off why are you asking about a sponge with the scubby part? Are you trying to clean the glass off? If so go to walmart or Home Depot and get a scraper with replaceble blades.