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Re: PCF light spread

Cavan, who grows many plants better than me, said:

> I have my 96 watt AH Supply PCF sitting right on the
> cover glass.  When I had Rotala rotundifolia a while
> back, some of it was directly under that light and
> some wasn't.  There was a line right through the
> stuff.  Stems on one side were red and green on the
> other.  It was as if someone drew it with a ruler. Not
> a gradual color change.  

Well, that's another way to test the spread of your lamps. 
The red color, being very sensitive to lighting, more
readily and clearly delineates differences in lighting
levels (other things being equal).  But this method takes
longer to perform than just holding the lamp over the floor
and using a ruler  ;-)  .  Finding a line at all with
fluorescents isn't easy because they are such diffuse
illuminators -- just look at the shadows they cast.

For most appplications, aquatic and otherwise, a
fundamental problem with fluorescents is getting some of
that light going up and sideways from the bulb, down onto
what you want illuminated.  The AH Supply reflectors, just
as they come out of the box, do an especially good job of
this -- maybe too good for some applications.  If you have
only one lamp or row of lamps on your tank, then you might
want to spread out the reflector a bit.

You can see strong differences in illumination by looking
through your tank the long way, through one of the sides. 
To do this, it helps to prevent any other lighting in the
room and to add a little calcium carbonate (CaCO3) to the
water to temporarily increase the turbidity.

BTW, does everyone want all of their tank to be lit up
exactly the same?  What's wrong with some places darker
than others?  Isn't aquascaping an art using plants *and*
light?  I ask this while admitting that I'm not much of an

Scott H.

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