Why do we need to change our light bulbs?

[Radicaljbr]

Could someone please explain why we need to change our light bulbs?

I have 2 250 watt MHs and I keep reading that they need changed every 6 months. Why?

If the light bulb is still working, why change it? Does it lose its spectrum or something?

Why not changing your light bulb cause algea blooms?

Thanks

[Runfrumu]

I was thinking MH last around a year. Basically they grow dimmer over time, and after a year or so they won't be nearly as effective.

[Art_Vandelay]

I believe it is due to a spectrum shift. The wavelength of light emitted from the bulb shifts toward the red end of the spectrum. No, your lights won't appear red ! However, the blue wavelength of light that contains the most energy and the one that is most frequently used by the photosynthetic algae within the corals will not be as prevelant. Even though the light may appear just as bright as when you first purchased it, the algae within the corals see a whole other light that they are not equipped to transform into usable energy and will begin to starve.

[Radicaljbr]

Okay, thanks

So why would aglea blooms start if not changing your bulbs on a regular basis?

Does bad algea like dimmer light?

[Art_Vandelay]

Oh... the algal blooms could result from the spectrum shift because some species of algae contain an organelle within their cells that allow them to trap red wavelengths of light instead of blue. These organisms would be better adapted to carrying out photosynthesis under the "new" light scheme and would begin to thrive. It's just evolution... survival of the fitest.
Keep in mind that algal blooms may be caused by many other factors as well.
I have read/ experienced that MH bulbs may last up to a year but best changed around 8 months. Keep good records and an observant eye on your specimens when that time comes to see what timeline works best for you.

[Radicaljbr]

Thanks

I do not remeber how old my lights are, but they are well over a year with 12 hour cycles. I also just restarted my tank in a new house after my rock and sand set in holding tanks for 6 months.

You can see my thread on setting up my new tank by clicking on my "red house".

I am currently having a brown algea outbreak which I am sure is from the new setup, but just wanted to ask about why changing bulbs, as I never really understood that.

Thanks again!!

[Art_Vandelay]

You're welcome. Your set-up is looking great... you must be excited. Good luck.

[celano]

Anyone have a link providing some data to back this up?
If mh's only last a year what about PC's or T-5's? Were any individual studies done for each type of bulb?

[Radicaljbr]

Originally posted by Art_Vandelay
You're welcome. Your set-up is looking great... you must be excited. Good luck.

By the way....I love your pose in your Avatar.

I know that is you and not Seinfeld!!!!