[Delphinus]

I don't know if I should admit this, but, I'm using a more-than-two-year-old 10000K Hamilton over my 20g which houses my green saddle carpet. If growth and colour of the anemone is any indication then as far the anemone is concerned it couldn't care less that it has an old bulb. I think, the higher the Kelvin rating, the faster the bulbs wear out and thus the emphasis on a regular replacement schedule .... but, some bulbs definitely continue to be useful after the prescribed interval .... Of course, I wouldn't go and recommend that anyone be as lazy as me when it comes to replacing bulbs, the basic rule should be whether you feel the bulb is working for you or not. If you have a lot of algae nuisance growth, or, you feel the light just isn't as bright as it once was ... by all means the bulb could be at fault.