well that answered your question.

You will see black around the base of the bulb that is a good sign of when to change it. Not because it is going to go out right away but you are loosing lumens.
Zandor Reviewed by Zandor on . Bulb changing If this has been asked before on here I'm sorry for asking again, but I can't find it :o I have been growing now for around six years and in all that time I have never changed the bulbs for new ones. I am using a 400 watt system and I use a metal Halide bulb for the vegative growing and switch to a high pressure sodium for inducing flowering. Now in all this time I have had rather good results and some decent crops, however the last crop was totally wiped out I suspect due to a blight of Rating: 5