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Re: Hot Lights

On my two tanks lit with 55w CF lights I have to use small (approx 2") 
fans, but not so much for keeping tank temps down but rather to improve 
lamp efficiency. I've never had to use fans on regular flourescents. I 
think the secret is to use enough proper ventilation that the lights can be 
cooled by convection. Leaving an open back and a small gap between the tank 
and hood will work, and somewhere I came across the excellent idea of 
installing duct grates (like used in houses on air ducts) on the top of the 
hood. Enough convection should be able to cool most flourescent hoods.

If you have to use a fan, you will want to use the quiet fans, which 
usually run on 12v DC. I have tried the so-called "smart" fans too, which 
sense the temperature and speed up as the temp rises. Either kind of fan 
can be found new from http://www.digikey.com and some of them can be found 
surplus from places like http://www.allcorp.com and http://www.meci.com 
(Mendelson Electronics). There are quiet AC fans but they are harder to find.

I suggest leaving a small space between your hood and tank and making sure 
there are some vents on the top of the hood too so that you can take 
advantage of convection. The heat of the lights will create natural air 
currents from the bottom to the top IF there is a way for the air to get in 
at the bottom and out at the top. I have a 400w MH fixture that is cooled 
by nothing but convection and it works great, so convection can be very 


>I have built three wooden light hoods during my short career.  The first
>was for a 120 gallon tank.  It uses an IceCap VHO ballest which is very
>cool, but the 4 110 watt flourescent bulbs are not so cool, and I found
>had to retrofit the hood with an exhaust fan to keep the temperatures
>78 degrees.

[more hot tank stuff deleted]

>The third was for a 10 gallon tank.  I used AH Supply's 2x36 bright kit
>with the 17.5 inch reflector.  Very nice kit.  Good bunch of people to
>work with too.  The lights raised the temperature of the tank into the
>stratosphere.  My liquid crystal thermometer didn't go that high, but I
>estimate it was body temperature or above.  I need to install an exhaust
>Exhaust fans are noisy.  My impression is that everybody else is not
>having to do this.  Please let me in on the secret.