When to replace flourescent lights?

[RockingCricket]

I asked this in the DIY section of the forum but am yet to get a response.

How do you know when a flourescent lightbulb has expired? I am under the impression that they should be replaced long before they go out. Is there anything to look for or is it just a case of being aware when it was installed, and replacing it say 6 months after that date?

 

[TLH]

The usual amount of time is 6 months yes.It can depend on what bulbs you have.I have some tubes that are meant to put out almost the same amount of light for their whole life.Only need replacing when they fail.I think they're Tritons.
If your tubes appear dull then they probably need replacements.

 

[wayne]

Well if they're going dark at the ends then they really are getting on a bit.

Fluors and MH lights react the same. As time goes by the blue part of the lights spectrum fades so the tube seems less blue, and less bright at the same time. I change mine every 6 months

 

[1979camaro]

i change my PC every 9 months but by that time the spectrum shift is fairly noticable, though i haven't noticed any negative effects on the tank of waiting that long

in your case, the tank is a fish only so it really doesn't matter how old the lights are because they are just for viewing the fish not growing corals/plants

 

[RockingCricket]

Thanks guys.