I also use refugiums with fresh water tanks, in addition to using the type of animals that help break down detritus into more useable compounds for beneficial bacteria and algae. I like to plant mine using floating and terrestrial plants like papyrus in open areas.
In predator tanks, small animals are usually quickly eaten, so a refugium is a great addition to the functioning of a more complete system.
Small shrimp, gammarus even small fish are all are beneficial breaking down detritus, and eating left over food bits. And protein skimming is valuable in systems where high protein, meaty foods can easily, and quickly degrade water quality.
My current tank is a 180, it uses 2 sumps , both function with partial trickle areas, both use algae scrubbing and have refugium component areas and contain higher plants, like the papyrus below.
I consider my 180 as a quite a small tank, so any help I can get in keeping water quality up is important, along with a regime of daily or every other day meager water changes.
My nitrate level goal is @5 ppm or less, and all these components help make that goal achievable