its VERY simple, just need a 5 gal bucket, either 2 bulkheads or uniseals, most people do 3/4" inlet, 1" output. fill the bucket till about 3-4" from the top with sand. feed the bucket to get about 200-250gph through it, and the output gravity fed back into the sump.
its worked WONDERS on so many tanks, and it cost barely anything to employ.
My nitrates are about 1-2, but im hoping this bucket polishes it off completley.