From Bob Fernner on WWM
http://www.wetwebmedia.com/plantedtk...ightingags.htm
A note here on Spectral Shift. As they are used, all the differing light technologies change to known degrees in the percentages of what wavelengths they produce. Their luminosity decreases also, along with the preponderance of the desired spectral bands
You are correct that metals along with other gasses all have a signature light pattern that they put out. 100% undeniably this is true. However what isnt taken into account in your arguement, is a point that i made in the first post, "That as a bulb ages, different gases and metals leave the bulbs at different rates." This is a well known fact. That is what causes the shift, is the ratio of different metals and gases in the bulb changes, as some escape faster than others.
It is this spectral shift that favors "undesirable" algae.
Also I am not debating the fact about a new tank getting algae blooms, this debate pertains to spectral shift, which occurs to a detrimental point after about a year or more.

To OP, sorry about the shift of this topic, but I hope you can find the information useful for the future when it is time to change your bulbs. Also I hope that you are happy with what you ordered, please post pics so people in the future can use your experience for help in their own bulb selection.