John,
Don't feel bad. I have no idea of how the PHP button on the menu works and I'm scared to find out.
I was somewhat tired last night. It isn't easy armchair quarterbacking all those games especially when they go into overtime.
I didn't answer you about putting VHO tubes in an NO fixture. Judging by a few responses I don't think I explained how a fluorescent works too well. The tube has an inert gas, argon, which is doped with mercury vapor. If you look at a fluorescent spectrum you always see a strong emission line around 330 nanometers. This line is cased by the mercury in the tube. The light from the mercury only is a small percentage of the actual output of the tube. Initially the ballast supplies a high voltage that ionizes the mercury in the tube. Once the bulb starts, addition liquid mercury is vaporized and the tube reaches full temperature. Electrons are emitted by the ionized vapor that then strike the phosphors and make them glow. The second duty of the ballast is to limit the amount of current that enters the tube. If current was allowed to enter the tube without restriction the resistance would fall to such a low level that an arc would form between the filaments and short the tube out in no time flat. The ballast prevents this form happening.
Now your NO bulb uses a ballast which allows around a half amp to pass. An HO allows a full amp and a VHO 1.5. If you use a magnetic ballast, which is usually the case in low cost fixtures, two problems arise. An NO rated ballast will not be able to run a VHO lamp. It will either fail to light or light only faintly. On the other hand a VHO rated ballast used on a NO tube will overdrive the lamp. It will run much brighter at the expense of tube longevity.
Electronic ballasts are a bit more versatile. They can be wired in such a fashion as to be able to run just about any type tube. If you are the type that likes to change things around all the time then they are a worthwhile investment.
Another thing worth noting is with T-5 vs T-12 run on a magnetic ballast is a T-5 ballast also runs at half an amp; the same as an NO T-12. A two foot NO T-12 runs at 20 watts and a two foot T-5 at 18. Since they both use about the same current but the T-5 packs the current into a smaller tube volume, the T-5 is rated as an HO and appears much brighter.
The thing here is that you cannot run a T-5 on an NO magnetic ballast. Why? Well the T-5 tube uses a different starting system than the T-12's. You need a ballast for T-5's to run them. This is a reason to always check with the manufacturer when selecting a ballast to work with a specific tube.
Another interesting point you made is about hood space. If one plans to go with MH lighting you need a tall hood. If you plan to start with fluorescent then upgrade to MH at a latter date you can always use spacers to lower the tube to near the water surface. When you then switch to MH you can remove part of the fluorescents and have the clearance for ventilation that a MH needs.
No matter what type of lighting you choose it is best to have a game plan. I have some comparison photos linked in this thread. They are OK but remember--a computer monitor varies from make to make. You really want to see the type of lighting you want in the real world of a reef tank. Look around at the LFS or at other reefers tanks.
Here's an idea. Find an established reefer who's bulbs are near replacement time. Con him into getting the bulbs in which you are interested. That way if your lighting scheme makes his tank look like a screen shot form a game of Doom you'll not be out the money.
You really need to watch your budget when selecting lights. It is great to get a megawatt MH/VHO combination but it can be a real shock to find the service to your house cannot support it. Using candles for lighting is romantic and you can always read the books you never had time to read when you had TV using the light from your tank. However, I think your spouse may draw the line when they must place buckets of water on top of your lighting hood to have hot water for a bath.
