Kevman Posted December 2, 2009 Share Posted December 2, 2009 Hey I am about to build my Canopy and thought(scratch) How High do I want it....Its going on my 75G I want to have 2 250w 20,000K MH's and 2 VHO 36" Actinic. With a 2 inch Sand Bed I will have 17 1/2 inches from Sand to top of tank.. I was thinkin about building it so I have the MH's about 9 inches above the water line... Is this to close? How close can I get to the water? I know Heat is a factor...... Thanks Guys I know you all will have some great ideas for me to chew on! (rock2) Quote Link to comment Share on other sites More sharing options...
finch6013 Posted December 2, 2009 Share Posted December 2, 2009 I have a 250w halide about 6 inches fromt the water and it does ok. But I have to keep fans blowing across the water. I think a safe bet that will also give good lighting would be 12''. Also you need to be up high enough for the reflector to give a good light spread. Quote Link to comment Share on other sites More sharing options...
nwcoralfarm Posted December 2, 2009 Share Posted December 2, 2009 12 is pretty much the standard, any closer and you get heat issues and any farther away and you lose light. Quote Link to comment Share on other sites More sharing options...
Rick Posted December 3, 2009 Share Posted December 3, 2009 There is very little light lost in free air with such short distances so it isn't going to make much difference if it's 9" or 19" regarding the light reaching the bottom. (Water depth on the other hand is a major factor) The biggest 2 concerns will be heat if the light is too close and positioning the light where it will cover the most area without too much light spilling out. I would say that 9" is probably far enough off the water to keep the heat away from the water as long as you are exhausting it outside of the canopy. Any closer and the heat will radiate into the water before it has a chance to be pulled away from it. My lights are currently at about 12" off the water through the winter to keep from losing too much heat (I'm actually using the lights to help maintain the temp) but early next summer I'll raise them back up to about 16" (A matter of just adjusting the length of the chains above them) to keep the heat away from the tank. Quote Link to comment Share on other sites More sharing options...
finch6013 Posted December 3, 2009 Share Posted December 3, 2009 If the light loss through the air is minimal then maybe I should raise mine, lose the fan and get a little more light around the edges? Seems not as bright when I lift the light though Quote Link to comment Share on other sites More sharing options...
Rick Posted December 3, 2009 Share Posted December 3, 2009 If the light loss through the air is minimal then maybe I should raise mine' date=' lose the fan and get a little more light around the edges? Seems not as bright when I lift the light though[/quote'] This has more to do with the reflector than the light itself. I.E. As you raise the light more of it spills over the sides rather than being focused into the tank which is why I mentioned it being positioned to cover the most area without spilling over. Quote Link to comment Share on other sites More sharing options...
nwcoralfarm Posted December 3, 2009 Share Posted December 3, 2009 Yeah I agree with that to a point Rick. Penetration is the biggest factor in light loss, but that is not to say that the distance of your light from the tank doesn't make a difference. Quote Link to comment Share on other sites More sharing options...
ThePremiumAquarium Posted December 3, 2009 Share Posted December 3, 2009 Kevin if it were me, I would have the lighting as close as I could while still allowing myself some room for the arm in the tank and a good light spread. I think it is important to maximize the amount of lighting that is focused down on where your corals are going to be. Your reflectors will play an important roll in deciding how tall you should build your canopy as well. Quote Link to comment Share on other sites More sharing options...
CCR Posted December 3, 2009 Share Posted December 3, 2009 If you have ever had a MH burn you'll know when your too low. Quote Link to comment Share on other sites More sharing options...
Kevman Posted December 3, 2009 Author Share Posted December 3, 2009 Kevin if it were me' date=' I would have the lighting as close as I could while still allowing myself some room for the arm in the tank and a good light spread. I think it is important to maximize the amount of lighting that is focused down on where your corals are going to be. Your reflectors will play an important roll in deciding how tall you should build your canopy as well.[/quote'] Thanks again Garrett, and thanks everyone for you thought and experience. I have a good idea on what I am going to do... first is get a new reflector... Then I think I'll have the bulb about 9 inches above the water with dual exhaust fans.... I'll post Pics to my Build thread once I get this completed(rock2) Quote Link to comment Share on other sites More sharing options...
Byrd Posted December 3, 2009 Share Posted December 3, 2009 Hey Kev, sounds like you're set on the heigth, an FYI I run 2-250DE MH w/ 4-65 actinics and my fixture sits 6 inches above the top of the tank, which makes the water about 8 inches from the bulbs-I have a chiller and yes it runs off and on all day. I pulled my fans since they did not make much difference and less clutter, but my build is different than yours. I have thought about lowering mine 1.5 inches as well-(nutty) Post some pics when its all done or thru the build. Good luck Quote Link to comment Share on other sites More sharing options...
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