Are you going to grow corals in the vivarium? If not I'd suggest a different bulb. I know they do 6700K, that would be suitable. I haven't tried saltwater bulbs on plants so I can't say for sure how poor the results would be, but they really don't produce a good spectrum for plants. I just checked and there is a 5500K which would also be suitable.

Plants like more red light, the almost pure blue light from your bulb will more beat them into submission than grow them. You might get some interesting results on alpines or dwarf succulents but generally I think you will get a disappointing amount of growth. If you want to try, you could always swap the bulb if things are not up to your expectations.

Isn't this power compact longer than your tank?

Its a quad so no its 18" long, the tank is 30, I've also got a dual that is ~36" long and 10000K that I stuck into a pot of soil and grew a scarlet runner bean with for a short while. should I be going for 67's or 65's rather than 10K's?

Thanks