The cold system is a very simple set up....almost an experimental system to see how the cold systems work out. There are two cold tanks....the main one (about 120 gals) .....and a smaller one that houses a few cold seahorses (about 40 gals). The two tanks are tied together through a common sump. Both tanks and sump are made from 1" thick acrylic to prevent sweating.
The equipment is just one Sequence pump that moves about 2000gph.... one Deltec ap600 skimmer......and one 1/2 hp chiller. Lighting is just a couple T5's over each tank. That's it....no Ca reactors or huge amounts of light are needed.
In general, these tanks are cheaper to run than a full blown reef since they require minimal lighting. The cold water seems to reduce disease as well. The most difficult thing is obtaining stock. There are a few critters that pass through our LFS that are really cold water....like catalina gobies.....red wartah anemones.... and several snails like red foots. I'm fortunate that I dive Puget Sound regularly and occassional bring back a shrimp, scallop, oyster, or star. And, like I mentioned, there is a cold water supplier in Australia....but, there are hoops to jump through.
It's a shame really....these cold tanks offer the beauty of our warm water tanks with less work and more room for error. It's really a chicken/egg thing.....there are no cold tanks since there's no stock readily available.....and there's no stock available since few have a cold system. Cold systems also suffer from the misperception that they are brown, ugly tanks that just house lobsters and a few ugly perch or something.