The Par 38s they sale at HD, Lowes etc are not geared specifically towards aquariums. They will grow the heck of Macro though.

Bulbs that I am looking at have been engineered for aquarium purposes specifically for reefs and planted aquariums. Come in more desirable spectrums 10k, 12, 14, 20k and full spectrum etc.. Not to mention each led is a 3watt where as in most you buy not for aquarium use have 1watt LEDS.

Some examples im looking into

http://www.boostled.com/product_p/par30.htm
http://www.rapidled.com/12-led-par38...color-with-uv/
http://www.ecoxotic.com/ecoxotic-par...ed-lights.html
http://www.ocreef.com/ocreef_par_38_..._aquarium_lamp
http://www.ledtric.com/led-component...-18w-reeflamp/