GPH loss from plumbing

I am workjing on my new 24g nano cube and want to split the output to 4 heads, all branching off of the main out through 3/4" exiting from directionals. I currently have a 400gph pump and was wondering if the pump would have enough pressure to be efective after all that travel? Is there a common formula for such? thanks.

 

I don't know the exact formula for flow I will try to find it in a fluid dynamics book on my desk at work tomorrow but I know from experience that 2 heads will cut down flow velocity by 3 times ( some thing to do with pie) compared to one head so four heads would cut each head down by a factor of 9 or maybe 12 the pump will still pump 400gph minus head but the exit velocity of each head will be slow. if you wanted a higher exit velocity a much smaller orifice at the end of each head would be necessary