If you don't have par data, a lot of fixtures tell you the lumen output, which is much more useful than wattage. The wattage per gallon rule is pretty useless even when comparing N.O. flourescent, with all the diffrent reflector configurations. If you want shimmer effect you need metal halide or LED pendant style. And don't be afriad of high lighting, you can always tame it back by adding tannins to the water, and/or floating plants at the surface. If you must have moonlights, you can always get a cheap add on actinic led strip to give you that.