Thanks Rosseau,
I had another google myself and found most of the same info. It seems that halogens are very much like other incandescants in that some, but not all of the wavelength is useful, but those that are not are well into the red range, which is really good for growing algae's, and then there is the enormous heat issue.
But I have found this very neat little halogen articulated fixture that I just may try on a 3 gal. pico and see how it goes.