Phoenix 14K PAR

Found this interesting since I use Phoenix bulbs.

The light output of the six Phoenix bulbs shows an initial decline over the first three to four months and then levels off at about 75% of their initial output. From these data I raise the question: “If a bulb is not replaced at six months, when it has lost 20% of its output, then why would we replace it at 12 months when its output has fallen only another 6%?” It may be more cost effective to plan the lamp number and placement based on 70-75% of the bulbs' initial output levels. Initially, we could shield or raise the lights and then gradually lower or unshield them over the first four months or so, when the intensity is at its highest but falls most quickly. Beyond six months the bulbs' light output remains fairly constant at about 75%, so only minor adjustments would be needed for at least a year. Doing this may considerably extend the bulbs' effective life.

I have been in the habit of replacing my bulbs about once a year as is so often recommended. The measurements suggest that this may not be necessary, though. In my aquarium setup, my lighting is suspended by a pulley system, which allows the lights to be easily raised and lowered (see Figure 3 below). Lowering the lamps a few inches can easily compensate for a 25 to 30% drop in lamp output to maintain a consistent light intensity for the corals by decreasing the distance from the bulbs. Having a reliable light meter, I can measure the output of all seven of my bulbs in fewer than five minutes. I now target a PAR level of 400-500 for the most light-demanding corals, and adjust the light pendants’ height accordingly.

Light Output of the Phoenix 14,000K DE MH Bulb Over Time by Allen Chantelois - Reefkeeping.com

 

This is an interesting point that you have brought up....
If someone were to ask me the question I would have said yearly also
That being said, "All lights are not created equal."
It is good that you have some data that you can go by to compensate for loss of ppfd or light intensity. However, until I see the data on the manufacturer of my bulbs I would still say once every year to 18 months.

It would be nice of someone to do this test on all of the common bulbs that reef keepers use above their tanks.
Thanks for the pointer on that article!

Jim

 

Good article.

PS: I LOVE my phonenix 14k's !!!