Kaptain Karl,
I'm by no means an expert but on the question of the kelvin temperature what I've read is that it's mostly about what your eyes like to see in the tank. My T5 fixture came with 10000K and it was just too blue for my liking, but a saltwater friend saw them and said they'd look great in his aquarium
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I've since switched over to 6000k Geisman bulbs and the lighting "looks" perfect to me.