A lighting issue I haven't seen talked about... Sharks???

[beattyr]

I was at one of the LFS last night and was talking about adding more light to my 37 gal tank. Specifically increasing with a 250W MH from the 110 pc I have now. He said I might need a chiller. I said I would plan on building fans into the hood to keep heat down. His reply was your tank still doesnt have much surface area so it can't dissipate the heat created from the rocks that absorb the light energy (being dark colored). I had not thought of this before. Is this something that has been taken into consideration with any of your tanks? Any thoughts on this?
Thanks
Rob

 

[saltyrich]

MHs will increase the temp. How high they are placed over the water level will determine this. Fans should definately help to control this. There is no way of knowing how much of an increase will take place until you do it. I would go for it. I think that in most cases temp. increases can be managed. An increase in your present lighting is of greater benefit here.

 

[jim672]

Rob,
I just replaced my old lights with a 175 MH and two 95W actinecs over my 45. The hood I bought (not good with DIY) has two fans that come on when the MH comes on. I had 3 40W NO bulbs before this and the new lighting increased my temp from 78-80 to 80-82....about 2 degrees.
With the fans, (and the glass lens cover)most of the heat doesn't actually go down into the tank, it gets moved horizontally across the hood and out. Also, I have the hood about 4 inches above the tank....maybe 5 or so inches above the water.
If you're considering MH bulbs, I would definitely recommend two fans. The place I bought mine suggested one fan with a 175W but strongly recommended 2 fans for a 250W or higher wattage.
Jim

 

[hondo]

I currently have a 37 gal tank and put in a 175MH retro light along with a 55w PC for actinic. The MH is only 3.5" off the water surface and heat was an issue until I put in a sump. It's amazing how adding the additional water surface area of even a small sump will cool off a tank. My tank temp stays at 80 with or without the lights on and no chiller is required. For added insurance a small fan blowing in the sump will provide additional cooling. Never thought about rocks absorbing heat from the light due to their color but it doesn't seem to be an issue with my tanks.