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Re: Light intensity

Subject: Re: Light intensity

George Booth wrote:

>I would like to see a discussion on two topics: 
>1) What level of lighting do the experts use (Tom, Roger, Neil, Karen, Erik, 
>Diana, Charley, Jon, ... you know who you are)?
>2) Why do many of you think "more is better"?  IMHO, more is never better. 
>More is trouble. Just enough is better.  

I have one perhaps interesting data point to share: I'm just getting
into planted tanks and have set up a 10 gallon to test out some ideas
found in this forum and others (Thanks!).  Of course I was so eager to
get the tank going that I planted it before I build the hood.  But it
seems to be chugging along fine with DIY CO2 under a 120 watt halogen 

Here's the interesting thing: because of the flood reflector, there is
quite a steep fallof in light intensity as you move radially out from
the center of the beam.  I can divide the area of the tank into 3
receiving different intensities:

1.  The center of the tank gets the best light and has a good crop of 
    algea going.  

2.  The outermost areas of the tank get the least light and have
    no algae, but plant growth (and pearling) seems quite a bit slower
    than the inner regions.

3.  Between regions 1 and 2 there is a ring that is algae free and has 
    plant growth and pearling equal to or better than region 1 !  This 
    region is quite clearly deliniated (on the inside) by the end of
    algae growth on the gravel (viewed from above, the gravel has a very
    clear disk of vibrant green algae in the center).

This seems to indicate that (at least under my water conditions) there
is a small range of light intensities which provide enough for plant
growth but not for algae growth.  Or something like that ...

My question:  Has anyone experimented with dimming fluorescent ballasts
or whatever to get into this lighting "sweet spot" across the entire
tank ?

Thanks for listening,
Alan Trombla
atrom at dnai_com