Fanning the Flames

[nosferatu51]

I'd always heard that putting a fan over your tank could lower your temperatures, but I'd never done it before. Yesterday I noticed my 75g was hovering around 83.5 (fortunately it's only 3 fish at the moment) so I decided it might be time to cool it down a bit. I put a desktop fan blowing up at the 2x250 halides. The temp, after the lights having been on for about 4 hours, is at 78.5. Wow, a full 5 degree drop (it may be able to do more, my heater is set to about 78)....I'm now a full supporter of this idea and thought I would give a little evidence for those who had never tried it.

 

[dc]

A fan can do wonders. I've used the cheap clip on fans from
Walmart. My hood now has a fan, so I don't need one.

 

[theop]

I like 80mm computer fans mounted to the back of the tank for this purpose.

Just be careful to watch your water level & salinity. You can evaporate a good bit of water using this technique. My 37g will evap about 1/2 gallon per day in the summer.

 

[RichConley]

<a href=showthread.php?s=&postid=8239365#post8239365 target=_blank>Originally posted</a> by theop
I like 80mm computer fans mounted to the back of the tank for this purpose.

Just be careful to watch your water level & salinity. You can evaporate a good bit of water using this technique. My 37g will evap about 1/2 gallon per day in the summer.

Theop, if you point the fans at the water, yes, thats true.

What the OP is doing though, is pointing the fans at his lights. I do the same thing on mine, and it hasnt really increased Evaporation much (a little). What it does do though, is moves all that heat from the lights away from the water. I had a 10 degree drop after adding a small fan that blows air out of my hood. The big difference wasnt an increase in evaporation, but in a large decrease in the temperature in the hood. It went from being probably 120+, to room temperature.

 

[stereomandan]

I thought MH bulbs like to run hot? Is this decreasing light output?

You might want to try pointing at the water instead. Yes, it will probably increase evaporation a little, but it might help your expensive MH bulbs.

Just a thought.

Dan

 

[stereomandan]

<a href=showthread.php?s=&postid=8239365#post8239365 target=_blank>Originally posted</a> by theop
I like 80mm computer fans mounted to the back of the tank for this purpose.

Just be careful to watch your water level & salinity. You can evaporate a good bit of water using this technique. My 37g will evap about 1/2 gallon per day in the summer.

Yeah, my 38g evaporates 1g per day, but I have an auto top-off from a 7g bucket. I only need to fill up the 7g bucket once a week with RO/DI water. One of the best things I ever did was buy that auto top-off, which runs off a float switch in the sump and a Maxijet 900 in the 7g bucket. The 7g bucket was just an old empty big bucket of Kent salt.

Dan

 

[RichConley]

<a href=showthread.php?s=&postid=8239697#post8239697 target=_blank>Originally posted</a> by stereomandan
I thought MH bulbs like to run hot? Is this decreasing light output?

You might want to try pointing at the water instead. Yes, it will probably increase evaporation a little, but it might help your expensive MH bulbs.

Just a thought.

Dan

I've never heard that they like to run hot, and honestly I dont think it will make a difference.

You're just moving the air outside the fixtures away, so the fixtures aren't cooking yoru tank.

 

[nosferatu51]

<a href=showthread.php?s=&postid=8239697#post8239697 target=_blank>Originally posted</a> by stereomandan
I thought MH bulbs like to run hot? Is this decreasing light output?

You might want to try pointing at the water instead. Yes, it will probably increase evaporation a little, but it might help your expensive MH bulbs.

Just a thought.

Dan

It is still warm under the bulbs, the air is just keeping that heat from reaching the tank (similar to a breeze across the ocean on a scorching hot day I guess). Keep in mind that, at least in my setup, the bulbs are encased in their own glass and then each is inside its reflector housing which again has a glass cover below it. The air is not reaching the actual bulb and if it is cooling anything, it is cooling that glass beneath it. I don't think blowing a fan at it, even if you blew it directly at the bulbs, would have an effect on the lights, but I could be wrong. Anyone know for sure?

I know the Kelvin temperatures are technically the temperatures that something runs at to produce that color, but I'm not sure if its a standardized measurement or if that's the actual temperature of the filament (which I highly doubt considering 14000 Kelvin is like 14000 degrees C ) I think it is really a reference color point and is used more as a descriptor than the actual measurement. Just an example: A magnesium core runs white at 10k Kelvin and therefore anything with that same color spectrum will be considered to have 10k color. Is that accurate and does it make sense?

 

[RichConley]

nosferatu, you're basically correct. Kelvin temperature ratings are the temperature that a blackbody would have to be to radiate that color of light. The problem is, actual color temperature of bulbs generally isnt all that close to what theyre rated at, hence why some 14K bulbs are bluer than others.

 

[nosferatu51]

How do you hook up the PC fans? I build computers so I've worked with them, but the connections wouldn't plug in to a wall socket correctly. Is there an adapter you can get or something?

 

[Chrisrush]

wall wort hooked up to the computer fan.