Geo is good, I also like Korallin. I've got a warning and two tips to pass along about regulators and pinch valves after I learned the hard way. First the warning. Getting your reactor dialed in can be very problematic and you will need to keep an eye on your pH, Calcium and Alkalinity until it stabilizes. How much calcium a tank consumes depends on how it’s stocked. The bigger or more stoneys you have the more calcium the tank requires. As your inhabitants change so will their calcium needs. This warning is related to the next 2 tips that are designed to make getting your reactor dialed in as painless as possible.
Don't waste your money on Milwaukee regulators, they are crappy. I went through two in less than a year and lost corals because it was impossible to get the thing dialed in correctly. I'd set it in the morning and by the time I got home from work it had stopped sending any bubbles through the bubble counter. So, I'd set it again at night but when I woke up in the morning there were no bubbles again. I had this problem with both Milwaukees and I wasn't about to buy another.
What I got instead was the regulator made by Reef Fanatics. It is awesome! I fully expected to have to spend days tweaking it before I got the bubble count right, but nope. Right after installing it I set the bubble count and went to bed. In the morning the bubble count was still the same. It was a true case of set it and forget it. And it wasn't a fluke. I've repeated this on several occasions after doing tank maintenance. The Reef Fanatic regulator is one of the best pieces of equipment I have ever purchased. They aren’t well known or easy to find. I got mine from aquacave.com.
As for pinch valves, I hate them. They control the flow of effluent from the reactor by literally pinching the effluent tube. It reduces the outflow to however many drips per minute you’d like, but they squish the tube and cause it to get clogged and very quickly you have no effluent coming out. The stuff gumming up the tube is the consistency of wet concrete and the tube itself gets compressed and it’s virtually impossible to get it back to its original round shape. A real pain to deal with.
As an alternative I decided to give a plastic airline gate valve a try and it worked like a charm. They are very easy to flush and reset. Just turn the screw, let the water rush through for 30-60 seconds and then close it again to reduce the flow back to however many drips per minute you want. They are also cheap. I got a dozen for a few bucks.
Another thing you may want to consider is your controller. I began with a used Pinpoint. It was OK but I wasn't crazy about it. Maybe I would have had a different experience if I'd gotten it new. With in a couple of months I replaced it with an Aquacontroller 3 which I like very much in spite of the big bucks it required me to lay out. I can tell a lot about what's going on in my tank with that puppy and I'm glad I spent the extra cash.