Originally Posted by Byron
In my view you will not have healthy plants with this light. I don't know the technical reason behind it, but I have never found one botanist or planted tank authority who has not said that plants will not manage under actinic light. It is obviously too blue and not enough red, but there must be more to it than that. On the other hand, algae grows very well under this (or any) light, so you will be battling that as well. Thriving plant growth makes life very difficult for algae. All the nutrients and CO2 will do nothing for the plants if the light is inadequate. Light is the single most important aspect of a planted tank.
You don't need to replace the fixture, just the tubes. And the best ones for planted aquaria are very inexpensive. You can buy "daylight" tubes with a kelvin rating around 6500K at most hardware stores for a few dollars. GE, Phillips, Sylvania all make them. The are no different in light colour and intensity than the much more expensive "aquarium" manufacturer tubes. Just measure the length of the existing tubes and buy the same in the other type. Make sure you get T8 if your fixture is regular fluorescent; a T5 fixture requires T5 tubes as the prongs are different.
In terrestrial plants, the bulk of their light taken in is 440nm (blue) and 660nm (red), and they both contribute to plants differently... Red is better for propogation, and blue is for fast growth. On terrestrial plants, actinic actually works (as long as the plants get some red..). Less evolved plants (ie algae) don't need the red, so they don't get slowed by the lack of it, and explode. Even if you scrape everything off daily and keep algae from covering the plants, there just won't be any nutrients available.
There's probably a little bit more than that, but that's as much as I know. Red frequencies help plants assimilate nutrients.