AFAIK, A MH light is meant to cover a 2x2 area so you should have a
fixture/reflector every two feet. I'm pretty sure a 220 is eight feet long
no? If that's the case, you should have 4 lights.

hth


~Mort

wrote in message
...

Hello;

I have a 125g reef right now with 3 x 250w iwasaki MH, 2 x 160w VHO
10k
and 2x 160w vho actinic. I'm thinking of going up to 220. I have a couple
of
clams doing well in the present setup as well as a variety of soft and sps
corals. Am wondering if I substituted 400 wat MH's with the same setup if
that
wold be suficient?

thanks

Bob