There are a lot of options, but you will need an inlet from your main tank, separate from the line to your skimmer/sump (the two systems in essence fight each other for nutrients to be removed from the water).
A means to pump the water back to your DT, which is where many options come to play. The pump could sit in the fuge or outside of it, the water from the fuge should go through baffles prevent chaeto from getting back to your DT, some add a filter here, others want pods to get back into the DT.