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Light Intensity & striking a balance

I'm curious about those of us using higher intensity lights on
planted aquaria. It would be interesting to learn the parameters
of our systems and what it took to reach that "acceptable balance"
(by which I imply a balance between amount of work (&$) vs.
the degree of niceness of the aquarium) Ok, now I have to define
niceness of aquaria: able to grow the plants we want and they
aren't covered over by algae. Often that is an either or situation;
lots of algae or so little that you don't notice its there.

I use a 250w MH light on a 75g tank which is 28" deep. I broke the
tank in from scratch using minimal fish populations and lots of
ottocinclus and some farlowellas. I have some Crypts and Aponogetons
and what I would term medium-high light plants that are all doing
well. I tried Cabomba in this tank but was not happy with it; too
long and stringy and far between the internodes. CO2 is a single
2 litre DIY yeast injected into the aerator of a powerhead. For me,
this tank is working (which means I have to do minimal algae
maintenance about every two weeks). Right now I'm using Flourish
weekly at about 2/3 recommended dosage per gal. The CO2 recently
measured was ~8ppm (lower than I'd wish). I added more sugar and
from pH I think it has improved quite a bit. I may add a second
yeast bottle but it may require less than the 49g; more to provide
a smooth(er) CO2 input. BTW, this is my vermiculite tank and
so far it is working beautifully. Very nice root growth from
many plants. Hard to say if its vermiculite, the earthworm
castings or the right amount of lighting (vs. depth of tank).

My other tank (49g) has a new 250w MH light. This is 18" deep tank
and the light was 18" above the water surface. I've moved it up
another 6-8" recently. This tank is not in balance and requires
weekly heavy algae maintenance. (see some of my recent posts)
CO2 was a single 2l DIY yeast which I will be doubling to two
bottles shortly. I don't think the CO2 is enough. My last measurement
showed ~5ppm and previously with glass covers and only 80w of
tired fluorescents, same CO2 I was easily maintaining +15ppm.
Both of my current tanks are coverless however I may put the
covers back on the 49g soon. The lighting period was 12hrs and
I have knocked it back to 8hrs. I will have to do a lot more
maintenance and wait a few weeks to see if this will make enough
of a difference. I want to increase the lighting period again
later once things improve at least to 9hrs and perhaps 10.
I will have to see which of my plants will be sustainable in this
tank. I will try some Crypts in a shaded setting at the far end
of the tank which is 4' in length.

I am very curious to hear both good and not so good experiences
from all those of you using high light intensities esp. those
who have Cabomba growing nicely. The discussions on defining
balance and steady state are interesting but I really think we
want to provide more pragmatic information for people wanting
to make changes. It is important to learn about what kind of
systems are attainable and also what didn't work. (OK here's
your chance to brag on your high-tech systems guys!)

Steve (on the high balancing wire) ;-)