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Re: low light tanks

Neil Frank wrote:
> >From: ac554 at freenet_carleton.ca (David Whittaker)
> >>I also have one tank with
> >>crypts, chain swords and "blood red" Rotala macrandra with ~1 w/Gal.
> >
> >I know that you have mentioned this before. I find it amazing.
> >Rotala macrandra requires a lot of (metal halide) light in my tanks.
> >What other conditions do you provide?
> This particular 70 gal tank (18"x48"x18") has a peat substrate (which is
> now over 5 years old); 


I'm curious, was this substrate always well-behaved, or did it have a 
break-in period when it caused you problems?  If so, how long did that last?

I thought this would be a good context to mention the idea of "balanced" 
and "unbalanced" growth.  I ran across these terms a few years ago while 
reading Gaudy and Gaudy's "Environmental Engineering".  They use the term 
to refer to cultured growth of bacteria, but it seems to fit well in 
aquatic plants, too.

Balanced growth occurs when growth is limited by available energy.  In 
plants that means light and CO2.  Unbalanced growth occurs with growth is 
limited by other nutrients - nitrogen, phosphorus, iron, calcium, etc.  
In plants, that can cause nutrient deficiency symptoms.

Plants grown under relatively low light grow more slowly than under bright
light, but in my experience they have fewer nutrient deficiency problems. 
I take that to mean that under lower light the plant growth is more often
balanced, but under high light it is often unbalanced.  Plants with
nutrient deficiencies aren't usually very attractive.  There are some
problems with slow growth, but if you can avoid the pitfalls then lower
light levels might make it easier to keep an attractive tank full of
healthy plants. 

Does that make sense?

Roger Miller