Yeah this tank is it's own system. We have a marineland sump, protein skimmer, refugium and UV sterilizer all plumbed underneath.
This tank has been in the store for years and years and has taken many forms (Goldfish WAY back when, freshwater rays, then the saltwater rays.) But it was never really a great tank, so we rebuilt it from the ground up.
We have Ca and Alk (I forget the brand) to dose, but since it's still a new tank, and most of the corals have been added fairly recently the calcium demand is still fairly low. There's hopes of a calcium reactor addition sometime soon too, when we get some killer growth and get some nice clams in there as well. I really like this tank for clams because you can view them from the top, instead of just from the side.