6700k or 18000k

[abcha0s]

Mix the bulbs. One of each.

If you can only have one bulb, I'd go with the 18K.

[gobytron]

euphyllia and lps really like the blue spectrum from what I have read...

plus, an 18k bulb is much less likely to promote problematic algae growth.



If it were me, I'd do a mix of them if possible and go from there.