quick coral placement question

[whites60]

I have 2 400 watt halides on a 90g and was wondering just how low I can place my hard corals and still get a good growth rate?thanks

 

[reefnut]

How deep is your 90g?? What kind of coral are you referring to??
I'm running 2-400s on a 110g and some sps corals a inch off the sand bed.

 

[whites60]

its 23 inches deep and then figure my lights are another 12 inches high. the hard corals I am referring to are acros. dig. pace. etc.