Do I need 150 or 250 metal halide lights

[parmoffitt]

I bought Coralife's Aqua Pro Metal Halide lights that sit on my 120 gallon tank. My sister has a 90 gallon tank with the same light system but her tank is a lot brighter than mine. I feel let down. I have had these lights for 3 months and still have the box. I talked to the LFS that sold me the lights and he doesn't seem to want to help me. He said if I put 250W MH on my 120 that I would need to buy a chiller.
Could something be wrong with my lights or should I have put 250 MH lights on my tank. I want the same brillance that my sister has in her tank.

 

[turningtim]

Is the 120 taller than the 90 and both are 4' in length? Are your corals doing OK? What is the color spectrum of each set?

 

[reefnut]

What are your 120g dimensions? I ran 2-400w MHs on a 60" long 110g without needing a chiller. A lot will depend on your setup.

 

[db]

I run 2x250's over my 72 bow with no heat problems. A few small fans will fix the problem unless you don't have ac in the summer.

 

[parmoffitt]

My 120 gallon is 48x24.5x25.5 and my sisters is 48x18x25. I think something might be wrong with the MH lights. They dim when I move the lights. The lights are only three months old
and I am going to see if the LFS will change them out for me or I will have to call Coralife.
It's good to know that I won't need a chiller if I have to upgrade to 250's. Thanks for the advice.

 

[hagfish]

The kelvin rating makes a big difference too. Typically, the lower the kelvin, the brighter the light will appear to our eyes.