How high should I hang my MH ?

[po2lony1]

Hi all I'getting the dual 250W MH soon for my 75 gal reef
I will bulid the canopy and I don't know how high should they above the water my water is at 80F now I dont want to rise the temp.

Please help me Thanks

[rtrice1]

There should be a minimum distance of 10" from the MH and the water. You will also have to install fans in your canopy to keep the temp under control. I have dual 250W MH on my 90 gal and I needed two 5" fans to blow on the water to keep the temp at 78 degrees.

[srit1]

if heat isnt a problem can MH lights sit 2" from a glass top?

in a 25g high I dont think light dispersal will be a problem either, so im wondering ar there other reasons to have them 10-12" away?

[po2lony1]

so the canopy will have to be tall which means it will be
heavy isn't that too heavy for the top of my tank?
and the fans where should I place them On the sides or on the top? and one more thing does the ballast also goes into the canopy which will make it even more haevier.
:(

[Leviathan]

Originally posted by po2lony1
so the canopy will have to be tall which means it will be
heavy isn't that too heavy for the top of my tank?
and the fans where should I place them On the sides or on the top? and one more thing does the ballast also goes into the canopy which will make it even more haevier.
:(

My canopy is 10" tall and its not that heavy, if I had to guess maybe 30lbs. I dont think you will have to worry about the weight too much as long as you dont go overboard.

I would place a fan on each end blowing cool air in across the water surface. Make sure though that there is some sort of escape vent on the backside of the canopy to help push the hot air out.

Most ballasts produce some heat, though e-ballasts produce next to none. You will not want to mount them inside the canopy though, the heat from the bulbs can damage the ballasts, and or shorten its lifespan.

[po2lony1]

Thanks for the info guys :rollface: :rollface:

[rpgraff]

How much is the efficiency of flourescent is lost in a combo light fixture (MH and FL) if the MH needs to be at least 10" from the water surface?

I would think that distance would work against the flourescent's ability to effectively light the tank.

[Fonchy]

po2lony1 do not put the ballast inside the canopy. ACCIDENT(FIRE) WAITING TO HAPEN), "ELECTROCUTION". What Im trying to say is water and electricity dont mix and if you have the ballast inside the canopy evaporation is going to do a nimber on the ballast or bow or whatever you have them in.

2 cents