Help me cool my top...

[fishy929]

I need to come up with some way of cooling my recently converted hood. For vision related reasons, I am forced to leave my 2x250W MH's about 4" off the water. This is ok except that I will soon be running into a heat problem as I run the lights more every day to acclimate.

Below are a few pics of my current setup. I am debating whether one or two 37cfm computer case fan venting up in the center of the hood would be sufficient in keeping most of the heat from building inside the hood and pushing down on the water. Alternatively, my wife suggested mounting a couple of 120mm fans just off the wall behind the tank, concentrated one per MH bulb between the hood and the water.

As you can see, there is no shield between the bulbs and the water. I had to remove it when I did the retro fit. I don't seem to have a problem with salt creep or splashing, so I'm not so concerned with this. However, it does limit airflow inside the hood from the two small fans that came with the hood.

What would be the best way to reduce heat on the water for this setup? Any advice would be greatly appreciated.

 

[wseaton]

I like the idea of the two 120mm fans sitting behind the lid and tilted blowing inward under the lights. Tilted slightly downward they'll also ripple the water under the MH's, and we all seem to like that effect.

A bigger problem would seem to be mounting those 120s in a way that prevented them from falling in the water. Note I've seen high powered 80mm computer fans that will push upwards of 80cfm, but they are noisy.

The biggest problem with having MHs close to the water with no protection is a chance of a splash turning one of the bulbs into a grenade. This close to the water they will also beam a tremendous amount of IR into the water vs the secondary problem of heating the air around them. Fans can't help this, but it's up to each tank config to see if temp is a problem.

 

[cleantank]

It also looks like you might be able to use the 4" fans, on the ends between the stands legs. From the pic's there might be enough room. Only draw back is it won't look as nice. But maybe better than fan's in the hood on top.
Let us know what you decide. 8)