Custom built acrylic tank (30 wide x 24 tall x 60 long) with an 80 gallon sump. The tank contains about 200 pounds of live rock with 2-3" of sand as substrate. The sump contains an eight to ten inch deep sand bed with macro algae and acts as a refugium.
Two 400 watt 10K German bulbs and four 48" VHO (three actinic and one daylight) driven by an IceCap 660 provide the illumination. The VHO's are on for 13 hours and the MH are on for 10 hours. The two MH bulbs are in reflectors from PFO and the VHO bulbs are reflected by covering the inside of the hood with "mirror" Mylar. One 18W PC is used over the live sand bed/macro algae sump, it's on 24/7.
This tank relies on live rock and sand beds to proved biological filtration. Macro algae is grown and harvested from the sump as another means of nutrient removal. A Red Sea Berlin skimmer, standard size, driven by a Rio 2500 provides additional filtration.
An Iwaki 40RLXT moves return water from the sump. The discharge is divided into two lines. A ½" line returns through a Sea Swirl return in one corner and a ¾" line returns water to the other corner through a flex fitting. One small powerhead (maxi-jet 1200) provides additional current on the side without the Sea Swirl. I plan on putting a second Sea Swirl on to replace the ¾" return soon.
A Kent 50gpd RO/DI system provides top off water via a dosing pump. The only additives I use are Combisan and iodine, both added once per week. I use a MRK2 model calcium reactor, loaded with Knop Korallith as media. No chiller is used and cooling is accomplished using two strong muffin fans. This results in evaporation rates of two to three gallons per day depending on the season.
More pictures of Todd's tank can be found on his site, http://www.teleport.com/~hillsont/reefs (Editor's Note: Site gone as of 04/21/04).