Haven't had any residue. I know it occurs because I read about it all the time. I do use only spring water without minerals, which might be the topic of another thread: Are there already minerals in natural spring water that help the frogs. But for this thread, the Microfiber Cloths grab so well, perhaps they also remove the residue before I see it. I also use them on my reading glasses, my computer, windows and even bar glasses. That's why I like the colored ones, so I won't confuse their use. I will keep the lemon juice in mind. That might be good also for refreshing the tank with a fresh scent. Thanks for the idea.