Changing bulbs

When does one know to change their bulbs on their lighting (besides when they burn out - that's for you Garrett!)? I have been running mine for about 9 months. What is the average life of a bulb? How do you know when they are not doing their job any longer?

LOL Damm you got me Val!! What kind of lighting do you have???

The best way to tell is using a lux meter.

Depending on the type of bulb you have, the time for changing them will vary. For any bulb two things happen with age. First is the PAR (photosynthetically available radiation) output drops below 100%. This would simply mean that the light output is not as much as a new bulb. This can be measured (like Jim said) with a lux or a PAR meter which run between $200-$900 or >. Based on the work by Sanjay Joshi (our nano-reef build judge) typically for metal halide lights the out put drops to about ~80% after 9 months and to ~70% about 12-16 months.
The second and most important issue is spectrum shift. With age the spectrum of a bulb is shifted meaning the Kelvin rating of the lamp moves to either higher or lower temperature after about 9 months for metal halide bulb. This can be measured with a simple lab spectrometer and is far worse than drop in light output. The reason being, it could promote the growth of unwanted algae in your tank. So most people replace their bulbs due to spectrum shift more than a drop in the light output.

As a general guide:

Power Compacts: 9-12 months
Metal Halide: 9-12 months
T5: 12-18 months
Any Actinic: 9-12 months

These numbers are off my head based on what I have read over the years.

Vishnu

i was told also that the older a halide bulb gets the more physical energy required to fire the light, any truth to that??

Well, the reason why I originally asked the question is because I have hair algae growth now, and there is a brown film on the back wall of my tank that was not ever there before. With the price of bulbs, I figured it was better to ask the dumb question than waste money on new bulbs. I think I will start with my Metal Halide...mainly for two reasons - I'm too uneducated to know what the other bulbs in my fixture are (yes, I am VERY uneducated), and second because I have an extra MH on hand. Anyone have any input for the idiot on what the other bulbs in my fixture are or how I can tell?

DO they look like these??
http://www.hellolights.com/ProductImageGallery.asp?ProductID=424&GalleryItem=1

What kind of fixture is it? Retrofit or one you can buy? If it's a regular light you can usually hit foster and smith or another company and they will tell you what lights goes with it. If you have actinics at all they last the shortest amount of time. Halides I change out yearly.

I checked the fixture when I got home. Yes, HD, that is what the bulb looks like. It is an Odyssea 96W?

That is the one you got from James at his meeting right???
is there 1 or 2 of them in there.

I would check out www.hellolights.com they have a good selection and are cheap as well.

Nope, I got that fixture from a guy off of RC (blankenship?). I've never gotten lights from James. It has two of those bulbs, 1 MH, and moonlights. I'm just really dumbfounded as to what to get. I want to order a light fixture for the 10G too if I am going to do the nano thing, but have no clue what I need there either! I'm so dumb when it comes to all of this...I'm amazed that my tank hasn't crashed yet! I'm just sick of the algae and need to GET RID OF IT! It is HA and it looks like the red slime algea growing on the back of my tank - UGH!! Any suggestions on the lights would be appreciated!

Is it a single end bulb(like a regular light bulb) or is it like a halogen shop light?? Could yo take a picture of it and post it??

These are a fair bulb for Actinics PCf for the money.
http://www.hellolights.com/index.asp?PageAction=VIEWPROD&ProdID=425

Does it look like this?
http://www.hellolights.com/ProductImageGallery.asp?ProductID=339&GalleryItem=1

what size is your halide? single ended or double ended? Realistically i would change them first if you are having algae issues.

I'll take a picture of the fixture tonight and post it. Should the 10G have a MH, or what should I be looking for there?

You could get a MH but IMO you shoud not need that much light. You could go with 24" T-5 but the only down fall is that a 10g is only 20". They also make a 20" 96w Power Compact that is nice. I am thinking about getting the 20" PC for my nano if I keep it running.