Hi, I'm new to fish keeping and have noticed some buildup on the walls of the tank. I'm wondering how to clean it? Sorry if that's a ridiculous question. In the past, when I was a ding-dong who didn't know what they were doing, I would do 100% water changes (cringe, I know, I know, I'm sorry) and would use a towel to wipe down the buildup off the walls. Now that I am no longer doing 100% water changes, I'm not sure how to clean the buildup off the walls. I don't have a vacuum (I don't even know if that's what you use it for or if that's just for gravel), so I'm wondering how to clean the buildup off the walls of the tank? Thanks!