its a never ending battle. They will always come back. But peeps around here say use RO/DI water to help with it. I live in Memphis, Tn and i use the tap water here and i maybe, and thats a big MAYBE have to clean the diatoms off the glass once every 3-4weeks. Even then its not enuff that its a big problem. I only have 5 snails so i know they arent cleanin the glass that well plus i would see "snail trails". I dont know maybe we have good water here but its workin fine so far.