How high should my lights be

[slick]

Hi guys I am going to get my MH bulbs and ballast on fri. YEAH. Any way I am taking my pc fixture apart so I can put 2 pc bulbs in front of my MH's and 2 behind them. I'm wondering how high should I put my lights off the surface of the water? I have a 90g tank with a canopy I just built. My lighting will be 4 65w pc's and 2 175w MH's. Keep in mind that I don't have a chiller and don't want to buy one. Oh yeah my canopy is 18 inches tall so I have plenty of room.

 

[shadow678]

I would suggest starting out at 10" from surface, and if that doesn't cause a heat problem, move them 1" closer and wait a few days to see if it is going to raise the temp. Keep doing this until you see a slight rise in temp, then back off an inch and there ya go. But this is just my opinion.

 

[adrian]

I agree, about 10" would be fine, any closer and you will not get very good light distibution, 8"-14" is the norm. HTH