How high MH from water surface?

[Griffer]

My reef is a 48x24x24 Envision acrylic. I have a dual DE 250w MH fixture that is currently about 5" above the water surface. A friend tells me that is too close, but not clear on what is the proper clearance.

The fixture is in a canopy, but heat is not a problem with two 120mm PC fans running. What would the proper clearance be? Thanks for any help.

Gene

[nanojg]

thats up to you, as long as heat, spread and intensity is ok than it really doesnt matter. my mh fixture sits right on top of my tank.

[mark54321]

I have mine 12 in. above the water level (2x250W), no heat issues this way