White balance on NikonD40?

I have a friend who has a Nikon D40. He is trying to take pictures of his reef aquarium, but everything is coming out really blue! I've looked into this, and it seems like the problem is that he needs to adjust his "white balance," but I'm having trouble explaining it to him without being there. He tried to adjust his white balance by taping a piece of paper to the aquarium and taking a picture, and it was saying, "not enough light." What can I do to help him with this problem?

Cheers, and thanks in advance.

He needs to read the procedure in his manual, because there are several steps.

To make a "target," he can put a piece of white paper (3-4 sheets, by the way) or poster paper (adequately opaque) on a table or counter and take the tank light and use that to illuminate the paper while setting the custom white balance.

Before all that, me might try just setting the camera to the fluorescent WB preset and see how that looks. Just press and hold the WB button and turn the command dial (thumb wheel) until the tiny fluorescent bulb icon shows up. He can also find this in the white balance menu.

Don't tape the piece of paper to the front of the aquarium. If you do, the camera will see the room lighting. Instead, tape the paper on the backside of the aquarium. That way, the camera sees the aquarium's artificial light on the paper.

Set the camera's WB to Pre and hold the WB button. The WB Pre should flash in the lcd. Take a photo of the taped paper. If the camera got the color balance, then the lcd should flash GOOD.

Here's a more detailed description of what to do.