nreefer ... T5 only lighting is usually placed within a few inhes of the water. T5 as supplement to halide is not that critical. My Halides are about 12" up, my T5's are 8" up above the water. Again, they are on Icecap ballasts and I only have 2 of them. The difference between halides with no T5 and with T5 is very, very obvious. You can see the T5's effect when I raise my light rack 2 feet above the water when I do maint. Again, the UVL super actinic T5's had a larger impact than the VHO when I was testing before I decided what to use as supplements. This was on HO ballast. With the T5's on the Icecap 660 it wasnt even close.
You would ultimately have to decide for yourself whether the additional impact of the T5 over the VHO is enough to be worth replacing the superior coloration of VHO actinic. I dont think that the UVL Super Actinic T5 on an Icecap ballast is lagging that far behind the VHO super actinic in terms of color. The VHO actinic has better color but the additional output from the T5 super actinic easily makes it the better choice fo me. It may or may not be the same for you. Again though, I dont like the T5 super actinic on HO ballast. Overdriven with the Icecap ballast I think its a good bulb. I think it's atleast worth trying if you already have an icecap ballast.
