two things i notice that i would change but arnt life or death and just personal preference
one is the emergency i would have it just above water level in your sump so that when its in use you know theres an issue , if its submerged youll never know its running only to look to see if water is goling down the pipe, if you plan to have a trickle going down it then run it just at the waters surface.
the other is i would feed my fuge with the return pump and a valve to control the flow , that ways your not diverting water away from your herbies drain and you can control how much flow you want in your refugium and fine tune it.
my 2 cents:P
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