set up question: min depth

[windcoast reefs]

I would go 18" at the absolute minimum. If its an 8 foot tank, you should really try and get it up to 20". Getting good flow can be really difficult in thin tanks. Without good flow you can get some nasty nitrate problems later in the tanks life.

[naesco]

Mine it is 7 foot tank .
It is 22 inches wide and probably 16 would be the minimum
My tank is only 20 inches high which give it a long sleek look

[e46er]

8 feet long any less than 18" will look so out of proportation.
My tank is 24" deep and wish it was deeper!