Re: [APD] re minimum light threshold

["S. Hieber" <shieber at yahoo_com>]

Is this with a white plastic reflector? If so, we might
expect weaker effective lighting than 1.5w under a very
efficient reflector. Borrowing form examples that are close
at hand, I have found that in a 20 gal with 36w of light,
Anubias do just fine even if substantially shaded by other
plants. Same for a 15gal with 26w.

Both of these are somewhat higher wpg than your case. And
these are set-ups with the highly efficient AHS reflectors.

In a tad smaller aquarium, with only a white plastic
reflector, my 12 gallon under 26w behaves like a very
highly lighted aquarium.

I wonder if the 7 watt bulbs might have the preponderance
of their output in the green range -- along with lots of
infra red, of course.

I also wonder is as much variation in wpg and the apparent
plant effects might be found among larger aquaria.

Could the small tank anomaly to the wpg rule of thumb
merely be an example of the softness of the rule in
general?

For me, whether 7w is a lot of light kind of begs the
question that I have in mind. It can mean a lot of
illumination in a small volume or for a small nearby
surface. 

If I put a plant in the 3/4g tank, 8" below the the bulb
and put another plant just like it in a 15g tank that same
distance from the water surface and the same distance from
a 7 watt bulb, then is the plant going to behave as if it
has more light in the 15g? The plant doesn't know what size
the aquarium is, does it? If not, then the size must be
affecting the lighting.

Scott H.
--- Rachel Sandage <rachelsor at hotmail_com> wrote:

> I read this thread with interest, because it seemed to me
> that common sense had completely gone out the window
> until someone pointed out that "7 watts is not a lot of
> light", which seemed to sum it up for me.  I can also say
> that even anubias will not grow in a 10 gallon tank with
> 15W of light, if that is the only light the tank receives
> - as is the case in my fry grow-out tank, which is in a
> photographic darkroom.
> 
> rs
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