Plants need full spectrum lighting. Believe it or not, not all lightbulbs include the full range of light spectrum that plants will need. Thus the reasons why there are lights made specifically for plants, reptiles, birds, etc.

Aquarium lights have higher output from what I understand - especially since the light required for aquarium plants must penetrate through the water.

I only keep low light level plants in the tanks that do have live plants - so normal aquarium lights rated for plants have worked fine for me and I don't need any fancy light set up (to boost light output).

Daylight Deluxe by Phillips are rated at 6500* Kelvin. Kelvin Degree's or K rating is the color temperature. From what I've read laboratory studies determined that freshwater aquatic plants (thats lumping all genus/species in one pile) do best between 5500K - 8000K (considered full spectrum lighting). They also determined that 6700K is optimum for steady and rapid growth. What it comes down to is bulbs with the 5500K-8000K have more of the blue/violet and red/orange colors of the spectrum which is what plants use. The green/yellow (mid-spectrum) are almost usless to plants, but that is the color temp. that is widely used in "standard" house hold lighting. These would be the soft white and cool white colors (3500K-4100K). These are used because to the human eye it is a comfortable range. It brings out more detail and color to objects for our veiwing and reading. The bulbs that are labeled Plant&Aquarium / GroLights usually have lower spectrum, arround 1600K-2500K, they have more the blue/violet and minimal red/orange. This is good for most low light plants like Java Fern, some Anubias and house plants (a big one would be african violets) It also helps enhance the colors of the plants and fish, almost like a blacklight. I have compared the aquarium/grolights to the daylight deluxe side by side and found that even with low light demanding plants the daylight deluxe will make the plants grow quicker and they seem somewhat healthier. This is good for aquariums that have herbivore fish like goldies and Mbuna's. My gourami's even would destroy a small plant over night, leaving nothing but a stem, maybe.----BUT---- As far as your particular problem. 1) The water may have an algae bloom (green water) that wasn't noticed with regular aquarium bulbs. Since the Daylight Deluxe are a more "natural" sunlight it may have brought it to your attention. Take a sample of aquarium water in a clear glass and hold it to the light to see. Also, did the water turn green as soon as you turned on the lights with the new bulbs? Or, did it take a few days to notice this? 2) Sometimes the tanks can throw a green hue when brightly lit, especially older ones. Do you have a "background" on the aquarium? A background (like the poster type at the fish store) will reduce this reflection greatly. 3) What I do (sometimes) is use a combo of the 6500K and "color enhancing" aquarium bulbs to bring out the fish and plants more. I have never had these bulbs make my water appear a spooky green, exception is an empty tank with no background and minimal decor (rocks, plants and gravel). 4) To answer your ? about cheaper aquarium bulbs, use the ones that say "Plant&Aquarium", I think thats what Skygee uses. Most plants will do better with the "Full Spectrum" lighting (5500K-8000K), some require the reds and oranges to stay healthy (especially any red/purple plants). For a descent article comparing lighting go to www.drsfostersmith.com search "fish articles lighting" and they have good color charts with the differences also www.ahsupply.com has a brilliant explanation, aside from reasonable retrofit kits that are superior to some of the top name brands. To add, Wal-Mart has 6500K spotlights that measure 6"X12" with 65W screw in type compact fluorescents for only $12. I just noticed them the other day. These are the same ones Home Depot sells for about$40. This comes with the Bulb and fixture, by "Lights of America" called "FluoreX". Replacement bulbs are only about $7 at Homo Depot. These are not "regular" incandescent replacement types. They need the ballasted fixture. I have used the screw-in compacts by this company before (incadescent replacement) and have also had great success.

To followup:

No my aquarium water is crystal clear! There is absolutely no "green water" bloom going on - but as soon as I turned on the fixture after installing the "Daylight Deluxe" bulbs I went yikes! at the green color. There is no background on the tank.And my tank was bought new less than two years ago so it is not an older tank.

I replaced those bulbs with GE's "Plant and Aquarium" lights (about $9 per bulb for 48")- I can't find the K value on the package for these. Somewhat better but still a noticeable green cast to the tank. I removed one of the Plant and Aquarium lights (its a dual tube fixture) and reinstalled the original bulb I had replaced (called "PowerGlo" bought it from a pet store, think they are by Hagen) and that improved things somewhat. It's still not the color I had before.

Now the only reason I replaced the original fluorescent bulbs was that I thought you were supposed to change them every year? Is that really necessary? I notice it says "nine year life" on the Plant and Aquarium lights. I'm reading on websites that the powerglo bulbs had a life of 7500 hours or so (varies with source). They're not that expensive ($11-$20 per 48") so maybe I should go back to those.

The "life" of the bulb is very long, Yes. Meaning it will light for whatever the guarantied years it is. The reason to replace them (I go 18 months, myself now) is that the phosphors become weak so the "effective life" is only about a year to 1 1/2 yrs. While the bulb will seem ok, its effectivness on plant growth lessens. When I change a bulb is when I really notice the difference. As far as the green hue, Try a background. Even just some poster black or blue poster board (or anything laying around the house, paper grocery bags) just to see if it makes a difference. If you look at the glass from the side (the thin side), you should notice that there is a green hue to it. I'm not sure why but it is interesting enough to research so off I go.

The green is from iron impurities in the glass. It may appear green to blue-green. Check out this thread. Someone has the same trouble as you. I put the link below. Just thinking about it, does your tap have a high iron content? Also, read the fine print the 7500 hours may be more accurate then years. If you keep your lights on for 10-12 hours a day for the plants the bulbs only will last 2 years or less, if they lasted exactly 7500hrs. For low light plants I wouldn't worry about it. Try maybe even mixing a standard (cool white or soft white) with the daylights.

Here is a link that might be useful: Interestin thread

I just read what I wrote up top and wanted to clarify:"From what I've read laboratory studies determined that freshwater aquatic plants (thats lumping all genus/species in one pile) do best between 5500K - 8000K (considered full spectrum lighting)." Instead of do best, I should have said look best. These type bulbs, 5500K-8000K, have alot of blue light which works like a color enhancer for plants in a way. The strong blue makes them look "natural" as apposed to the Plant & Aquarium (P&A)lights. The P&A lights do great for growing plants, mostly red spectrum, usually 3100K and below, but make the plants look "off". They usually have that purple hue and the greens look black, to me anyway. I use them usally in the ratio of 30W full spectrum over 10W P&A. This is my preferance, but know people who prefer the P&A only. Most prefer the 6700K. The bulb you had originally was 18000K, very white/blue. Great for reef keeping butnot enough red spectrum for freshwater plants. Will they grow with this spectral light, yes. Just not as efficiently. I still say try to mix the daylight deluxe with the P&A. That would probably benifit the plants photosynthesis best, may not look so good though. Beauty is in the eye of the beholder type crap.