I am thinking of making my 20 long into a diy sump for a future 75 gallon build. I plan to place baffles with one section containing a skimmer. My question is whether it's worth using a refugium in this build or save that space in the sump for other forms of filtration. Will a small refugium in a 20 long really contribute much nutrient export in a 75 gallon tank or is it simply too small proportionally?