Demystifying Lighting and Burn-in period

Subject: Demystifying Lighting

> Instead of trying to figure out theoretically how much light rea
> plants, with all the complications that entails, why not just ge
> meter. Wrap it in plastic and hold it where your plants are. 

Easier and less expensive still is to use the very workable rule 
of thumb, and watch your plants.  They themselves are a very good 
indicator of adequate light levels.  It's interesting to measure 
things, but I think we need to pay more attention to the response 
in the plants themselves.

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Subject: Burn-in period

> >I have a 45G tank ( 36x24X12 ) with a twin bulb shoplite ( yes,
> >inches )  The bulbs are GE wide spectrum, 5 months old. At firs
> >tank was mighty bright, but now it's not. 
> All fluorescents have a burn-in period when they give off up to 
> light than they're designed to over the long haul. At 5 months o
> lamps might be finished with their burn-i period and are now pro
> light they're rated for.

The burn-in period for T-8's is about 100 hours.  You should hit 
that in a couple of weeks.

> You need more lamps, not newer lamps. 
> When designing your lighting, look at the "design lumens" or "av
> lumens" rating for the lamps. These are what you can count on fo
> more.
> Have your plants grown in the 5 month period? If so, they could 
> your tank too.

These are all factors to consider, but here's another.  Very often 
cheap shop lights come with very cheap tar ballasts that seriously 
shorten the life of the tubes placed in them.  It's possible that 
his tubes are burning out prematurely due to faulty ballasts.

Karen Randall
Aquatic Gardeners Assoc.
Boston, MA