Useful life of 20K XM bulbs???

[Derek B]

Anybody know what the useful life is? I am wondering if I need to replace mine ... I've had them for about 10 months???

[Instar]

You are nearing replacement time. Max time on the correct ballast is 1 year. JimD may have the exact % of deterioration and how many hours you need to reduce photoperiod by with the new bulbs, if he sees this.

[Derek B]

You mean I need to reduce photoperiod on replacement bulbs because the ones I have have deteriorated?

[Instar]

Yes, new bulbs will be much brighter and stronger. They will cause bleaching in most cases if you stay with the same photoperiod because the corals can tell the difference in the amount of light output. New bulbs will be at least 30% brighter and stronger after the initial burn in period, even if they are the exact same type as what you already have. Light bulb materials, filaments, etc. deteriorated when used. They generate UV. Perhaps that is part of the reason they degrade over time. Same applies to florescents as to MH. The time of useful life is not the same for all brands of bulbs. You just happen to have the XM's and they are good for longer than some others. The hospital I used to work at replaced the florescents in the used for therapy after 750 hours I think it is. If we only run them 12 hours per day, thats a replacement every 2 months. They get replaced when they hit 30% reduction in output, basically.