light gain & environment temperature

Hi everybody,

following the recent thread concerning efficiency of light reflectors I would
like to make a remark. I recently bought a (German) book "Handbook Aquaria
Technology". It describes at length the technical details about lighting,
heating, filtering etc. with a lot of tables and graphs. One of the most
interesting books that I saw in this area, a lot more technical than the 
"Optimum Aquarium".

It amazed me to read that the light gain of neon fluorescent tubes is
strongly dependent of the environment temperature the tubes is running in.
There was a little table:

environment temperature (Celsius)     light gain (%)
            0                            35 
           10                            80
           20                           100
           30                            95
           40                            90
           50                            85
           60                            75
           70                            70

As you can see, 100% light gain is only reached at 20 Celsius environment 

The book also mentions that most hoods are not ventilated enough so that the
environment temperature of the tubes is often higher than 50 Celsius. Just to
check: 50 Celsius is when you can still touch the tube with your hand but
only for a short time.

This was certainly true for my hood that I used before I switched to high 
pressure mercury vapor. Shouldn't we maybe think more about hood ventilation
in addition to optimize reflection?

BTW, the book's second edition that I bought was released in 1992. The author
is Hanns-J. Krause. In one chapter on aquatic soils he says "In 1968 I(!)
discovered that natural aquatic biotopes are usually spring areas. ...
This lead me to recognize the importance of soil currents for aquatic plants". 
But Dupla is not mentioned once in the book. There are a lot of pictures of
Dennerle products, though. Unfortunately the background of the author is
not described. Maybe he is working for Dennerle. Did you ever hear his name?

The illumination theories also differ quite a lot from the Dupla 
recommendations. He speaks about occasional "rain days" and such. I will cover 
this in a later post, if you are interested.

Andi from Munich, Germany (where we have one day spring and the next day winter)