Ok, so let's try to figure this out. First off, camera brand doesn't matter. The thing is, a zoom lens isn't what we normally use to shoot things in the tank. A true macro lens is what you're looking for.
In your pm you asked about using filters. I do not use them. If you shoot in RAW format, you can adjust the white balance in post with either the software that comes with the camera, or with Photoshop.