The Planted Tank Forum banner
1 - 10 of 10 Posts

·
Premium Member
Joined
·
1,885 Posts
Discussion Starter · #1 ·
Do lights shift up or down in K as they get older?

I recently had one of my 8month old 175w MH bulb burn out on me. I got a new one (same brand, watts, and K). After I replaced the burnt out bulb and had both MH lights running that there was a pretty noticeable difference between the two bulbs. The new one appears more yellowish and the older one appears bluer. Both bulbs are 6500k. I thought the colour shift was downward and not upward. I think I will just replace my other old bulb also and just keep it around to use later since I don't like the look of the two colours on the same tank.
 

·
Registered
Joined
·
166 Posts
IMHE the tend to get yellower with time. I believe even if you have (same brand, watts, and K) they could have different manufacture variations, same bulb diferent batch. They should be pretty much the same but this things happen.
 

·
Registered
Joined
·
1,315 Posts
Anyone who uses or interested in using MH really should be familiar with some of Sanjay's tests and articles: List of all my articles

The shift is usually not that percievable to the eye. Its not really that the spectrum is shifting, its that the intensity is dimishing over time, and sometimes unevenly. If the output of the bulb dimishes more in blue than yellow for example, it results in a slight shift overal towards yellow. Here is a bunch of info Sanjay did for color shift during burn in and over the bulbs life: Aquarium Frontiers On-Line: Feature its also worht noting that for bulbs in the plant range (like the Iwsaki 6500K) that several 1 yr old bulbs actually produced more PAR than the new ones did, indicating that the shift is lesser than the difference in consistency from bulb to bulb.
 

·
Premium Member
Joined
·
1,885 Posts
Discussion Starter · #6 ·
Well I switched out my old bulb with my other new one so that I could have both new ones figuring they should be the same....they weren't. The two new bulbs are different colors. One of them (2nd one i replaced) looks like my old bulb and the other does not (very yellow/green looking). I have contacted Hamilton Lighting to see if I can get it replaced. Guess it was just a faulty bulb and not a color shift.
 

·
Banned
Joined
·
5,009 Posts

·
Registered
Joined
·
1,315 Posts
No, youd have to maybe search around his articles and read more. I beleive that the article was done when maybe there was only 1 type of these bulbs (hense the lack of any other id), I could be mistaken. I havent used MH but have done lots of research as I have considered it for my next plant tank.
 

·
Banned
Joined
·
5,009 Posts
Thanks for the info.
 
1 - 10 of 10 Posts
Top