6500k is very YELLOW, great for macro alage in a sump or for coral growth in a frag tank, but not very pleasing to the eye for a tank. Most lights are a combination oo 10k (10,000) and 03 Actinic. That allows for the dawn - dusk effect where you start with just the very blue Actinic lights for an hour, tun on the the MH
for about 10 hours, turn off the MH
, then turn off the Actinic an hour later. Some folks just have 12k, 14k or 20k MH
. The higher the temp the bluer the light.
For a 55g depending on what you want to grow you should get a 6 - 8 tube T5 with individual highly polished parbolic reflectors for each tube, or 150w or 250w MH
combo wiht T5 or PC
. Or, you could break the bank and buy a totally controlable LED
unit like the PacificSun units I just bought.