MH DE bulbs

[kimoy]

how do you know it's time need to change your bulbs:question:?

 

[hibye]

when the bulb starts to turn black

 

[bobby]

I think the only for sure way is using a light meter to check the par or something, but I would just stick to every 6 to 12 months.

 

[Bifferwine]

When your corals start dying off ;)

 

[reeffreak]

Without a lux meter to know for sure then 6-8 months is the norm.