First MH Lighting - question about the height

[lastduke]

20G Tank, Tank Height 15inch
70W MH pendant temperature 20K

How high from tank this light should be placed?
It is 11 inch from the tank right now. Is that too high?

I use the MH light first time.Thanks

[zack85]

depends on the temp of water and how the corals respond. You can prob take it lower to about 6-8'' but keep it high enough that you don't get a spike in heat

[lastduke]

I don't have coral yet.....I make the process slow.....waiting for the MH light working first, like you said no temperature spike then put the coral in

[jgiannini]

I have 2 x 150 Watt MH bulbs over my 38 gallon tank with 2 fans that blow 70 cubic feet per minute and I don't see any temperature issues...and the lights are only about 3 inches from the water....but I do need to top off daily with fresh RODI to make up for the evaporation. 70 watts seems a bit low to me for that tank. What types of corals are you going to keep? I'm just not sure if 70 watts is going to be enough. Have you thought of using T5 lighting?

[chrisqueenz]

A few inches off the water's top should be fine...

[bertoni]

I think that a few inches off the water is a good guess.