Hi.
My fluval (remember its old) needs 40.7cm for the tank then the doors are 36.5cm when fully open. Also you may want an external filter which will stop it being flush against the wall which will add ~3cm.
Heres a quick video I just shot of my shoe string setup.
That is so awesome! Not sure I could manage a salt water setup, but that's brilliant what you have there
Thanks very much and for the measurements!
G
/edit why do you say it's shoe string?