What camera do you have? Some cameras (even non-SLR) have screw on attachments which can help with Macros.
My camera is an SLR but I didn't want to put in the money for a Macro lens, so I bought some tubes. I fit the tubes to the camera and then the lens to the tubes and it works great. It basically extends the internal range or the lens and makes it a macro. The only downside is that the focus range is really small, but I manually focus anyway on the fish as they're scared of the light.
If you don't have an SLR, just check if your camera has a macro mode you can switch to. It'll normally look like a little flower symbol or a flower symbol with a magnifying glass on it. Most cameras have this mode somewhere.