Turnover is the number of times water passes thru the container in an hour, be it fish tank or fuge. Say you got a 20g fuge and a sump rated at 20g gph
. Assuming no head loss from running the water up a certain height and the sump actually pumps 20 gph
, then your turnover rate is 1x. I think I'm going for a slow flow like that in my fuge, maybe 2x.
By contrast, reef tanks are suggested for a 10 - 20x turnover rate. Return pumps and a combination of either powerheads or closed loop systems get you that high.
Not sure about the mineral vs. miracle. Probably similar if not the same. Just a guess. Google'm.