i use a lights of america utility light, supposed to be the same as a 500w incandesent bulb. so far i've had good luck out of mine, lots of growth on the chaeto, retpo and probably a few others here got theirs from my batch. not sure of the kelvin rating of the bulb, since mines been burning 24/7 for nearly a year im sure its taken a nose dive which is why the algae grows so well. algae like other plants grows better in the red spectrum of lighthing which is why the 2900 gives better growth than the 5100, thats moving into the yellow white color. as for the disclaimer its partly for the reasons listed above but its also a disclaimer so you cant sue the sand company and say they didnt tell you not to use it in an aquarium if something happens and your tank crashes. i've heard that some home depot stores have directions not even sell you the sand if they find out its for a fish tank. someone posted something about that on rc once.