it is small, the one error i made in the design was that i measured out the shelf heights without taking into account the width of the cross beams taking up a fair bit of height. But having used it for a few days now i can say its enough space to do everything easily, a few cm less and it would be a mission but there's just enough space to get your arm into the tanks on the middle shelf, more space on the others, and the daily water changes, feeding are easy without having to stick your arm in anyway. Have got 3 of the middle tanks in and filled, sitting on constant 20deg, bottom tanks are 26 with the heaters so i'm fairly pleased with the heat keeping. Just chucked a spare tank on the top, will fill that today and see what temp it sits on up there.
Will grab some more photos later