OK, so without getting mean, arrogant or just plain bratty, explain why, (in quantifiable terms not subjective) T5 is better vs T12 for supplemental lighting when used with leds. Keep in mind the following: I have the stuff to DIY a 4 bulb retrofit for either size bulbs. I already have access to two dozen 24" t12 bulbs that are unopened. I have access to almost a dozen 24" t5 bulbs that are unopened. We are going to use 24" bulbs as a comparison because the wattage is nearly identical and it's the size that will fit my cube. Space is not an issue where this is concerned Heat is not an issue where this setup is concerned The bulbs I have are close in spectrum (actinic and 6500K) They actually look close to each other. All we are doing here is eliminating some shadowing One other thing, when using t12 you can actually overdrive them with electronic ballasts and get more power but shortening life a bit. So we may explore that avenue It matters not, that it's old school technology. I ran t8s and t12s for years with nice results as a primary source of light on many tanks. So saying because it's newer or older isn't a good argument. All though this is for fun mainly, I may just implement some of the stuff discussed here. I will be open minded to all suggestions/opinions but data rules the day here.