Krause's lighting theories
some of you requested details on the lighting theories of Hanns-J. Krause's
"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.
* 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 the
water surface during the morning and evening due to the angle.
* 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
- One rain day once a week
* Krause recommends to introduce one rain day per week with only environment
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.
* My own experience: I never tried it. Well, raindays occur, for sure. But
this seems to contradict the target that many of us have: Plants have to
use up the different nutrients/waste materials that build up in the water.
- Plant lights should have a high red content. This is most important for
* Krause says that red light is the most powerful light for photosynthesis.
Unfortunately it is absorbed quite fast in the water column so that
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 TROCAL neon
fluorescents and HQL bulbs. In fact, they do emit quite high red contents.
I am looking forwarding to hearing your comments.
Andi from Munich, Germany (where storms build up again)