Topoff to display or to sump?

I am currently topping off my evaporation with kalk.  The kalk is pumped
into the display tank using a medical pump.  I also incorperate a sump for
my setup.  The sump contains my euroreef cs1, the refugiumand the return
pump.  Does it make any difference at all to pump kalk in the display tank
or in the sump?

tia