I am in the middle of putting together a few tanks for some doctors offices and I had a few questions. My first concern is this, many of these offices want to have a tank maintenance free. They don't want even feed the tanks, but will probably have to. what size sump would I need to have for say a 72, 90 or a 120 gallon tank, in order for them not to have to top off the system within the month. They will be getting monthly maintenances, so I plan on taking care of this at that time. Most of these offices don't have any extra rooms or access to a basement, so it would have to be built underneath, in the stand. I plan on putting in automatic dosers for offices that want reef tanks. so I'm just wondering what the best solution would be for them. all help is much appreciated.