I have the 94L version and the fans annoyed me too. I actually bought new PC fans and changed them over (honestly not as hard as it looks, just need a little screwdriver) but they're still a bit noisy. However the tank warms up quite a lot with the lights on so you seem to need the fans.
Here's a good link to help you change the fans:
http

/www.interpet.co.uk/wp-content/uploads/2011/05/River-Reef-48-fan-instructions.doc
I had to modify a bit as i went along. Basically unplug everything going into the hood, take out the main light tubes, remove the support screws from the hinges, lift off the hood and flip it upside down on the floor/table. There will be a white and black plastic cover which keeps the condensation away from the circuits and lights. Remove all the little screws holding it in place, and carefully remove it and lay it to the side. Slowly and carefully because the wires for the main lights and leds are attached to it so you can't move it far! Then you'll be able to see the circuit board and follow the correct lead to the fans (or fan, there might only be one in the 48). If you just want to disconnect it, simply unplug it a bit like a phone. However once you're up to this point it's easy to change the fan, just remove the four screws holding it in place and put the new one in label face down, and plug it in, use a small cable tie to tidy everything up. Replace the plastic cover and screw it back on tightly.
I didn't have a clue when I started trying to fix mine but I understand how my tank works a hell of a lot better now! Fortunately my boyfriend is a computer geek so I had help!
I think you might even be able to fix the fans on the 48 without removing the entire hood, I can't find the link I had to that, but you can just google it. If there is a panel on the top fixed on with small screws then it can be done, but you'll need to hunt for instructions!
As for the fans themselves, I can't find the ones I bought and can't remember what spec they are, but when/if you remove them just google the numbers written on the label. After a bit of hunting I got them on eBay for about £7 each. Mine aren't that quiet but if you wanted to spend more you'd get better ones. Just make sure they have the correct attachment for the circuit board, I think it needs to be two pronged, but have a look when you take them out.
Sorry for the essay! Hope that helps
