Old Bulbs = Algae

[Myka]

Originally Posted by chris88

The shift in spectrum isn't the issue with old bulbs, it's the major drop in par. Its on average about a 30% drop in par after 6 months and sometimes a 50% drop after a year. This happens with t5's or halides. This isn't a debatable issue. There is a lot of data on the decrease in par so its a fact and not a conspiracy. I would not suggest running any type of bulb for longer then a year unless you are doing a fowlr tank. I change my t5's at about 9-10 months.

It is a debatable issue because your numbers aren't right, but that's a different topic. Please explain how lower PAR affects algae growth...?