Originally Posted by AdamsAquarium
Not true that those "red or blue" lights cause algae. Aquatic plants need a good mixture of reds and blues. Normal fluorescent bulbs have both of these but you need a 2/3 ratio of reds to 1/3 blue. You probably will not see the reds of blues but it is on the bulbs descriptions. The reason for it is the reds need to be a longer wavelength and the plants absorb it faster than the blue, which is what gives it it's color. But when the red is not absorbed as quickly as the blues are, that's when you start to promote algae growth.
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Not true that "red or blue" light won't cause algae. If you were in the Freshwater section, that'd make sense but this is in Saltwater and it's a bit different. (It was originally posted in salt because it was supposed to be a cheap alternative for coral light). Too much light period will promote algae no matter the spectrum.
Red, Yellow, and Green that make the 6,500k look will promote algae more. You also need excess nutrients though.