I've only tested a few T5 lamps and that was years ago and I'd have to see if those companies are still around. Those lamps producing light skewed towards the violet end of the spectrum would be my choice, along with a pure actinic, a green one (if its output is less than 550nm) and two daylight lamps. So, 2 -violet, 1 - actinic blue, 1-'pure' green, and 2-daylight. This should cover the full range of the chlorophylls/chlorophyll-peridinin complex and should work well if PPFD (PAR) is at least 100, preferably a little more, in the darkest, unshaded areas in the tank. Using violet and green lamps in lieu of the standard actinic/daylight combo should stimulate photosynthesis quite well since their spectral peaks are outside of the absorption peaks of protective xanthophylls.