which one first

[Capt.Nemo]

so i bought my first reef ready tank and sump. not real educated on the whole sump subject and still nervous about it.
the question....
which one do i fill first?

i know, how dumb am I

 

[Bryson.bobby]

Fill both of them up, no specific order. Fill the sump until the return chamber is ~3/4 full. Then fill the display until it starts overflow and kick the pump on.

@ me if you have any further questions