cheeks...very good points!
And some tanks (tall tanks) also have a smaller ratio to water volume/surface area for function and will have a smaller bio-load capacity with all other things being equal.
I would opt for a dsb in a 40 short before I would use a dsb in a 40 tall
as an example:
30x12x=360x3" =1080 cubic in
36x18=648x3"=1944 cubic in
Quite an increase
Steve