how to calculate water flow

[sebastiaan153]

so im in the middle of designing a reeftank and im wondering how to calculate the amout of water that is able to flow trough the gaps. its a tank of about 200 liters and want 40x flow so about 8000l per hour. how do i know these gaps are big enough.

 

[KStatefan]

This will estimate the flow thru a toothed weir

Rectangular Contracted Weir Calculator

Google Sheet