Why would a bulb shift color at times?

[OneReef]

I just changed over to two Aquamaxx 14K 175w SE bulbs a few weeks ago. They have been a nice blue color. I came home today and one side of my tank was blueish like normal, and the other looked pink/red. I turned the halides off for about 15 minutes then turned them back on. Now they are back to normal. I had this happen when I had XM 20Ks for about 3 months. At the 3 month time, one of them shifted to that red/pink color, and stayed that way. Is this a bulb or ballast issue?

 

[mmagaletti]

The color produced by the bulbs was to do with the current running through them and the filament. If the filament is damaged to get a color change. If the ballast is not working properly, you can get a color change. I would try switching the malfunctioning bulb with the good one. If the problem follows the bulb then you have your answer that the bulb is bad. If the problem still occurs in the first fixture with the new bulb then you know it is a ballast issue.

Cross your fingers and pray it is only a bulb issue. This is a lot cheaper fix