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Substrate longevity

Bill Lynn wrote:

>For what it's worth, I set up my first Dupla tank about 88-89, the tank
(350L) has
>been set up in it's current position since August 1990 with Dupla cables,
>transformer and controller. I have not had any substrate problems ever. I
>George mentioned he vaccuums his substrate ( the top layer)
>is something I do not do. The only time a disturbance occurs is thinning the
>plants (especially eh giant Val.)

I wasn't in any way suggesting that a tank with Dupla cables WASN'T stable
long term... I would expect it to be.  It's just that I've seen excellent
long term stability in tanks without cables as well.  The limiting factor
in my experience has been the substrate becoming root bound.  If you're
growing a lot of plants in a confined space, it's going to happen sooner or
later.  There have been times when I've found that I can no longer even
work my fingers into the substrate of a tank through the root mass.

IMO. there are two ways of handling it.  You can get the whole thing
completely root bound, in which case, you make such a huge mess pulling
everything up for division that you might as well start over (been there,
done that<g>) or you can periodically pull up and divide just a section of
the tank at a time.  Claus Christensen suggests gravel vac'ing the area at
that time.  He says that plenty of laterite gets left behind.  But even if
you don't just pulling stuff out by the roots decompacts that area.  I
suspect that the root parts that get left behind just rot and turn into
plant food.

I may be wrong, and, George, please correct me if I am!<g>  But my
impression from watching George's video is that he does a fair amount of
uprooting when he does his regular maintenance.  I suspect this is how he
avoids the problem of root bound substrates.

Karen Randall
Aquatic Gardeners Association