Fan Noise
 

I've got a Coralife 250 MH setup with a built in fan. I'd like to reduce the noise level a bit.
The fan is out of the unit right now so if anyone has some great ideas please let me know.
The fan is 120 mm square and 120 volt.

you can get 120mm x 25mm and 120mm x 38mm computer fans. They are 12VDC so you'll need an adapter but they should be quieter, usually around 29dBA.

I concur with Sphelps...but you can also get replacement fans from Coralife and it will probably be quiet for a while before it too gets noisy.

If you go with the PC fan option, there are several good fans out there that are really quite quiet. You could also put more than one fan in as I found multiple spots when I opened my fixture. Since you have to re-wire the DC fan in anyway, doing two is just as easy.

I agree, replace the fan...

I have the same unit, and mine is quite, I don't hear a thing. You can go to Memory Express (2 locations in Calgary) and get one there, most likely will be under $10

Your old one, the bearings are probably worn out or faulty.

Idon't know how these fans look, But I had a computer fan that started to make noise.
I peeled the decal off of one side, and put a drop of thin machine oil onto the bearing.
It would stay quiet for about 2 months and then I would have to repeat.
Any thin oil would work. All depends on the condition of the bearing. It does not take much oil!

Many fans have sealed bearings, so I wouldn't recommend oil, as it may not work well, but also hat oil could get into your tank. Fans are cheap, so I would just replace

I agree...oil is just too risky.

You certainly do not want oil to fall into the water. That is why I said just a little. You could always put oil onto a toothpick and apply it like that.
But you are right, these computer like fans are cheap. And that is why you won't find any with sealed bearings

All the fans I have ever purchased are sealed, and over the years I have bought many as I own a web hosting company and have a half decent sized data centre so keeping fans on stock is always necessary... Go to Memory Express, get a Sunon fan, they are the best and will cost you about $10-15 for the one that fits the canopy.

I'm good with the computer fan idea but correct me if i'm wrong. I have to convert 120 Volt AC to 12 Volt DC. There's no room in the unit to accomodate any kind of transformer to step down the voltage. The issue is there are three power cords coming into the light. One for the MH bulb, one for the Actinic and one for the lunar lights.
There's really no room to put in anything else.