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Micronutrients
I wanted to make an early report on micronutrients and see what your views
might be. We had a wonderful visit with Claus Christensen here in San
Francisco a week or so ago. Claus' consistent observation whether it was
the research planted tanks at the Monterey Bay Aquarium, my tanks, Dave's
tank, etc. was that the tanks he saw needed more micronutrients. In my
case, Claus pointed to paleish new growth of Sagitaria subdulata and Crinum
calistramatum as indicators of the micronutrient deficiency.
Now it may surprise some of you to learn that many of us here in the San
Francisco Bay Area are quite conservative about nutrients in general, and
nutrients in the water column, in particular. I was trained by Karen who
always taught us to use 'just enough' and not more, and to use our eyes to
observe our tanks. :-)
With this in mind I have always dosed Tropica Master Grow conservatively. I
use about 30 ml per week in my 125 gal. tank. Water changes are around 40%
per week or 10 days with very soft water, very pure Sierra water. Our water
has been so soft this winter with the extra rains, that some aquarists have
reported pH crashes. KH has tested under 0.5 degrees in at least one tank I
have been helping with.
With 30 ml a week and sufficient other nutrients I have had good growth and
healthy vibrant plants. However, I have routinely observed that fast
growing runner plants, E. tenellus is perhaps the best example, and a few
others will come in a little paleish looking and then green up in a month or
so. I simply thought this was typical, or even, 'optimum'. :-O
During Claus' visit he mentioned that in his soft water experimental tanks
in Denmark he was using much more TMG than the recommended dosage. He sort
of whispered that he was using maybe even 3 times as much as the recommended
amount, but that he could not put such a statement on the label. He also
confirmed that TMG was designed for use in very soft pure water (as well as
for harder water, richer nutrient conditions). I asked Claus if increasing
the TMG dosage would result in more algae in my tank and he said flatly that
it wouldn't.
So with a bit of hesitation, 10 days ago I doubled my TMG dosage to 60 ml
per week. I have one of these Eheim Liquidosers so I programmed it to add 2
ml. 4 times a day starting just before the lights come on and ending a few
hours before they go off in the evening. So these nutrients hit the tank
just as the light cycle fires up and the plants need them, and they continue
to be available throughout the day. Better conditions for the algae to grow
in as well, right Roger? That's my view anyway. With a dose every couple
of hours at least the TMG nutrients are not limiting, I would have thought.
The result: Plants are growing very well and coming in much greener. To
use one of my favorite scientific terms, the tank has even more 'sparkle'
than before. The growth is not faster, just richer. And to my amazement,
there is even less algae on the glass (the plants have always had very
little visible algae on the leaves). In fact, almost no visible green algae
on the glass after 10 days. What on earth could the explanation be? I'm
guessing Roger would say toxicity of one or other nutrient, if he agrees the
micronutrients are not limited. But I wonder. Why doesn't the usual modest
compliment of green algae grow on the glass under these conditions?
Any ideas?
Steve Dixon in San Francisco