The picture on the left obviously has more blue color, whereas the picture on the right has more yellow.
The reason for this is probably the fact that your camera has been set to auto white balance. When you meter off and almost similar area, but if there is a slight tilt to the camera, there is a chance that the readings will differ and the camera compensates accordingly. This results in the difference color cast.
As such, on higher end cameras, you can actually specify the color temperature in the settings. So...if you are using ADA's FL tubes for example, set it to 8000K and all your pictures will come out color corrected. Do remember to set it back to normal when you are done, otherwise your regular pictures will look odd.
Hope that helps.
Cheers,
I have dwarf cichlids in my tanks! Do you?
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