This is why I like pictures. Now I feel like I understand your tank. You just can't describe in words the things learned looking at pics. Very nice shots.... glad you included equipment, drain lines, etc.
I bet that brown algae on the back glass of your display is driving you crazy as an eye sore. Just give it time. When your alkalinity and calcium levels become more stable as you develop a buffering and dosing routine, and you start to see coraline spread, that brown algae will be a thing of the past!