The lights you may need will be dependant on the types of photosynthetic animals you will wish to keep. How many/much will depend on tank size and depth.
In general terms, high output fluorescents (PC
, T5HO) will support a wide variety of corals including soft, LPS
and a few select lower light SPS
if enough intensity.
If the tank is especially deep or the sessile invert preference was primarily SPS
and clams, you'd be looking at MH
or and MH
w/actinic fluor combo. MH
is effective in a 2'x2' area so tank length as well as depth must be considered including the height the lights will be suspended, generally 8-12" above the water line. For most tanks 250w MH
(upto 36") is usually sufficient but shallower depths can use 175w (upto 24") and deeper tanks may require 400w (upto 48" or more).
Decide on what you want to keep in the tank and then the lighting needs would be much easier to decide on along with the tank dimensions.