Originally Posted by smiles
Yes I do have plants, and I was asking about the bulb as a grow light. I wanted to know if there's anything different from a bulb marked "grow light" at the pet store or if it's just a 6000k/7000k flourescent tube like any other. So from what's been said it sounds like the "special" pet store light bulbs are no more than a gimmick, which isn't surprising. That's good to know about the bulbs losing intensity with time, I'm sure it happens so slowly that I'd never notice and wouldn't have known. Thanks!
I think there might be a bit of confusion in this thread, over what we are each meaning. You can't compare apples to oranges. There is quite a difference between fluorescent tubes depending upon the phosphors coating them, i.e., how they are made. But the "good" tubes from the hardware store are just as good as the "good" tubes at the fish store. But you need to understand what makes the tube "good."
The "grow light" as you call it is in my view a poor tube. These can include some pretty expensive brands, like Hagen's Aqua-Glo and Flora-Grow, or the much less expensive plant and aquarium tubes made by GE, Phillips, etc that are available at the hardware store. They are weak in intensity, and being red and blue they produce a purplish hue in the aquarium. One may or may not like the hue aspect (I don't), but the intensity is very significant for plant growth.
The scientific evidence that aquarium plants grow best under full spectrum/daylight tubes is well known. These generally have a kelvin between 5,000K and 7,000K. But intensity is even more important. Fortunately, these tubes tend to have higher intensity, along with the better spectrum. And here you can compare the expensive fish store tubes with the much less expensive hardware store tubes, and find comparable tubes that are just as good. At this point, you are comparing apples to apples and oranges to oranges.