Re: Krause's lighting theories

From: hermel at ibm_de
> some of you requested details on the lighting theories of Hanns-J.
> "Handbook Aquaria Technology" in comparison with Dupla's "The
Optimum Aquarium".
> Let's discuss the following suggestions. IMHO they differ from what
Dupla says:
> - - Too much light is harmful and can cause cyanobacteria. Better
use weaker
>   light and longer duration. 
>   * Krause says that in the tropics you mostly find a light cloud
cover in the 
>     sky and waters with aquatic plants are often in tree shadows.
So light is
>     not as strong as we assume. He recommends light durations of
slightly more 
>     than 12 hours to prevent algae.

I don't think this is true across the board.  I've seen a lot of
video footage from collecting trips and such and I saw a LOT of
direct sunlight areas.  I would also disagree that in the tropics it
is often cloudy.  From personal experience I can claim that it is
exactly opposite of that.  Storms occur frequently but are quick to
arrive and quick to depart.  It also depends on the season.

>   * Dupla says that short light duration and strong light are
better because
>     O2 saturation is reached earlier. 8-10 hours are even
sufficient as in the
>     tropics, you have a 12-hour day but the sun is reflected from
>     water surface during the morning and evening due to the angle.

I've been following these recommendations with incredible success. 
I'm currently using four 110W VHO fluorescents on my 75g and two 175W
Metal Halides on my 120g.  I light the tanks for 9 hours per day.

>   * My own experience: Cyanobacteria are getting worse in my tank
>     since I switched to more powerful mercury vapor lights (about
50 lumens per
>     liter) but I still suspect that this is due to a NO3 deficiency
so that
>     phosphates cannot be used up.
>     Increasing light does not help alone you also have to balance
macro- and
>     micronutrients accordingly.

I would agree with that completely.  If you increase lighting, you
need to increase CO2 and nutrients.

> - - One rain day once a week
>   * Krause recommends to introduce one rain day per week with only
>     light to give the plants a chance to recover. He claims that
plants look
>     better after such a day. O2 content has to be monitored
initially though.
>   * I never saw such a recommendation by Dupla.

I have not tried this either.  Dennerle suggests a break in your
lighting every day.  Once a week is more reasonable.  I have seen no
scientific information that plants need rest.

> - - Plant lights should have a high red content. This is most
important for
>   photosynthesis.
>   * Krause says that red light is the most powerful light for
>     Unfortunately it is absorbed quite fast in the water column so
>     plant lights should emit a high red content.
>   * Dupla says that the light spectrum is not this important for
plants as they
>     grow in nature under different conditions (tree shades, colored
water etc.)
>     and they are cabable to adapt. Light intensity is much more
important to 
>     support photosynthesis than light spectrum.
>   * My own experience: I had the best results with the Dennerle
>     fluorescents and HQL bulbs. In fact, they do emit quite high
red contents.

I agree with Dupla.  Intensity is the most important.  There are
folks out there growing plants under the most unusual types of bulbs
so spectrum doesn't seem to matter.  I'm a firm believer in that you
can get plants to grow with any type of light as long as its balanced
light.  Balanced with your levels of CO2 and nutrients.  If any of
the three get out of balance two things can occur.  Algae or
deficiency symptoms.

So do you live in Germany?  I'm a big follower of Dupla's methods as
I have had a lot of success with them.  I admire their products as
well but many are not available here in the US and the ones that are
available are prohibitively expensive.  I would kill for a pair of
their HQI pendants!  I also admire their glass tanks.  Have you ever
seen their glass tanks?