Awesome! Thanks Mike!
You'll have about 75W of LED load, plus inefficiency of the drivers and whatever the Arduino uses (from the 5V reg on the shield). I'd suggest a 24V 6.5A supply so you have some overhead available for the Arduino and some fans to keep the LEDs cool. This MeanWell 150W unit is what a lot of the reef keepers use:
That controller project you saw is a SparkFun.com proto-shield with a ChronoDot from macetech.com, plus a DS18B20 OneWire temperature sensor and fan controller I built for a customer. It works with the Power LED Shield for scheduling and thermal management of the LEDs. This: http://www.chestersgarage.com/store/arduino-shields/fan-temp-rtc-proto-shield/ You talk to the ChronoDot within your sketch to get the date and time. It also has the 1-second square wave pin assigned to pin 2 so you can get an interrupt every second. It's not really specific to reef tanks, and I'm going to make it into a another shield/kit as a nice addition to the Power LED Shield for any project. But I'd be glad to build the proto-shield for you if you're interested.
Mark