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How to Increase Light Levels (long)


Hi everybody,

I realized that the two 38 W neon tubes (with aluminium reflectors) over my 
tank do not supply enough light. The water column is 40 cm high, 
50 cm is the total tank height. Length is 120 cm, width is 40 cm (240 liter 
tank, about 65 gallons). The neon lights are one Triton and one Dennerle Trocal.

Generally, plant growth is rather slow although I inject CO2 (with automatic
PH control, PH is 6.8 at a KH of 4 and a GH of 5 so CO2 should be sufficient
according to the tables). Nitrates are about 12 mg/l and phosphates are
almost undetectable (just the first color on my test scale, I forgot the 
exact value). I also control Fe regularly and I aim at 0.1 mg/l although it's
sometimes too much and sometimes not enough. 

Fertilizers I use is the complete Dupla system including Laterite (and nothing 
more) in the ground and Duplagan against Mg deficiency.
There are also heating coils in the ground therefore I think that all 
conditions should be optimal for the plants and that the limiting factor is
the light. I have one corner in the tank where sunlight reaches the tank for
about an hour per day. In this corner, E. tenellus and E. bolivianus are
doing much better than in the rest of the tank where they are not
growing well and therefore developing some algae problems. But not in this 
corner!
I remove each week some looooonnnngggg green thread 
algae which are fortunately relatively easy to remove and I do a 30% water
change each week with pure R/O water where I add hardness with Dupla 
KH/GH-Bildner. The fish load is rather low (2 discus, 12 neons and some catfish 
and SAEs). Temperature is 27.5 C, about 81 F). The tank is running since
4 months now. I have 12 hours of light per day.

As after all these investments I really like to see some real plant growth ;-)
more according to the Dupla/dutch tank type I now think about exchanging my
light sources. I spoke with our local pet shop owner who is really quite 
knowledgeable. He told me that according to the "Optimum Aquarium" book, I
need 8-10000 lumen over my tank for very good plant growth. I checked it with 
the book, it's true. He basically pointed out four directions to me and we 
discussed also the different lumen per watt numbers for different light 
sources as given in the "Optimum Aquarium":

1) Extend the neon lights in the hood to 3 tubes.
   + Cheap to operate
   + Relatively cheap investment
   - produces too much heat, especially in summer
   - light will still not be in the 8-10K lumen range
   - hood will not really fit anymore

2) Place three so-called Dupla "Sparlampen" (= saving lights) over the open
   tank. They contain the typical energy saving bulbs and good reflectors and
   have a rather good spectrum.
   + They only consume 18 W each - about 100 Marks a year total with our 
     electricity prices.
   + They are still relatively cheap (200 Marks each)
   - Together, they only produce something like 4-5000 lumen - not enough
   - They are not strong enough to provide high light levels at the tank bottom

3) Place two 80 W Dupla HQL lights over the open tank.
   + Together, they are in the 8-10K lumen range.
   + Lights can also be operated with 125 W bulbs if needed.
   + Sunrise effect
   + Provide high light levels at the tank bottom
   - He showed my the HQL spectrum in a book. Seems like HQL bulbs have too 
     much red - Promotes algae growth?
   - 160 W together - about 200 Marks electricity per year
   - The Dupla lights are ugly - big and brown
   - The Dupla lights are expensive - 400 Marks each

   * I could also buy cheaper lights but they usually have worse reflectors so
     that less light would reach the tank bottom. Therefore I would need two
     125 W HQL bulbs instead of two 80 W bulbs for the same light level at the 
     tank bottom and that would lead to about 350 Marks for electricity per 
     year.

4) Place two HQI 70 W lights over the open tank.
   + He showed me the HQI spectrum in the book. He told me that they have the
     best spectrum for plants and also prevent algae because they do not have
     much red - True?
   + Later, I could use HQI lights for a saltwater tank after replacing the 
     bulbs and security glass covers. My dream is to have a saltwater tank 
     sometime.
   + Together, they are in the 8-10K lumen range.
   + Provide high light levels at the tank bottom
   - 140 W together - about 200 Marks electricity per year
   - About 1000 Marks for the lights
   - Bulbs are more expensive.

What do you recommend? Is this all overkill for such a relatively small and
shallow tank? What are your experiences and comments?

So far, I tend to go for the HQI lights because of the good spectrum, the 
useability for saltwater and the high efficiency.
If I have to spend money then I rather like to spend it for something useful
in the long term. I followed all the talk here on the list about VHOs and
such. It seems like we do not have equivalent tubes here in Germany. Or is
my Triton already such a tube?

My intention is to discard the factor that I consider to be the limiting
factor for "real" plant growth in my tank. I would like to see fast plant
growth to limit algae growth as much as possible. Again - what are your
experiences? Do I have to expect a slowdown in algae growth or even more
algae growth if I increase the light levels so much? Then I would 
think about it again because my real intention is to limit algae growth
by improving plant conditions as much as possible. Or do the plants have to
"outcompete" the algae again? Should I maybe start with 7 or 8 hours of 
strong light per day carefully so that the conditions are only changed slowly
and the plants can adapt? What are the experiences of those on the list with
HQI lights and algae?

I did not write much about the plants I have. Well, I have E. tenellus,
E. bolivianus and E. rose, Alternanthera reineckii, Limnophila sessiliflora, 
Vallesneria spiralis and driftwood with Anubias and Javafern.
But I want to replace them with faster growing species anyway time
after time when the new lights are installed. But I have to watch temperature 
requirements because of the Discus in the tank. In the Amano books I saw that
it is possible to have nice plants *AND* Discus. Or is this a dream?

Sorry for the long post. I admire the collective aquatic plant care
intelligence here on the list and hope that you can give me some tips.

TIA Andi from Munich, Germany.
hermel at ibm_de