Best K rating for reef tank lights

[fkshiu]

Any discussion of colour and growth potential with respect MH bulbs in purely general terms is pointless without reference to Sanjay Joshi's testing:

http://www.reeflightinginfo.arvixe.com/

Choose your ballast, choose your bulb and off you go. PPFD (a.k.a PAR) and CCT (a.k.a. colour) are the most important columns. Actual power consumption in term of watts is useful as well.

Of course colour preference is purely subjective and mixing in supplemental lighting such as actinics adds to the choices you have.

Having supplemental actinics gives you more flexibility since you can use a bulb with higher PAR which are GENERALLY in the lower-K more yellow range.