You sure you don't mean T5's? The reflector is the key behind them: it is designed to really punche the light down into the enclosure (each bulb is housed in its own reflector). They've been using them for years over in the UK, but have only hit the states in the last couple years. Here is one of the best suppliers in the U.S. for them: http://www.reefgeek.com/products/catego ... ofits.html
I should be installing a T5 retro over a reef tank in the near future. Will let you know what I think.
Robb - I know what you're talking about. I use T-12 but I've been thinking about switching over to T-8 when i build my next viv. I have seen them - they are at home depot. I buy my 48" T-12 tubes there. I use a mix of Phillips' 5000K and 6500K. They work great. Phillips also makes the same exact bulb in T-8. I have only seen these at home depot though.
I'd suggest the T-8 over the T-12 any day. The only reason I use the T-12 tubes is because I already had the fixtures. The T-8's put out way more light without having to overdrive the fixture (Which I have no idea how to do, so I don't.) Plus the T-8 fixtures are actually a little cheaper at home depot than the T-12 fixtures.
The bulbs are about $3 or $5 each and a 48" double tube fixture will only set you back about $15, so you really get a lot of bang for your buck. If you try it, let us know how it goes.
Only I can't seem to find out if they use a different ballast or if it is just a different type of bulb. Nor can I find anyplace that sells them. With 100 lumen per watt they are the efficiency of a T5 HO, just less wattage.