Looking for caculator for bulkhead size

[TheReefGeek]

Ok, so does the calculator assume there is no weight for the flow rates it spits out then?

I am not a physics expert, sorry if I used the wrong terms.

In my basic knowledge of physics, isn't one of Newton's first laws f = m * a, or force = mass times acceleration? Force is aptly named as N, for Newtons.
And water having mass, being pulled down by gravity at 9.81? m/s squared, will create force. That force when partially blocked at a bulkhead would create pressure, pressure expressed as Newtons per square inch? Maybe there is no pressure right at the bulkhead, just the surrounding glass?

I'm not sure, I just think you can put more through a bulkhead where there is more water sitting on top of the bulkhead than if there is none?