[tang daddy]

Good answer ^

And now from my own experience if you have a tank with low depth like say 18 inches a t5 54w fixture may grow sps however for a deeper depth it will keep stuff alive but not thrive!

I had a 6 bulb tek over my 120g with 2 extra single t5's full sps tank and in 3 months went back to 2x250w hqi. While some sps did well with t5 at the 8in and up mark the rest coloured down, so IMO mh hqi with sps FTW!!!!!