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Re: roots, nutrients

On Mon, 26 Oct 1998, Steve Pushak wrote:

> Consider an analogy of houseplants which become rootbound. They do need
> to be repotted periodically. I think its often suggested that the roots
> themselves should be trimmed when repotting, "to encourage new root
> growth". I don't know if there is validity to that but the idea of
> pruning roots in the aquarium has been mentioned once or twice and
> perhaps we could discuss that idea?

I once uprooted a C. balansae for replanting and found roots 4 feet long
(infertile substrate, UGF).  How the heck would you replant that *without*
trimming roots?  That is a pretty consistent problem; some plants develop
roots so large that it just isn't practical to replant them without
trimming the roots.

Steve also wrote:

> A few more mud questions:
> Do worms play an important role in the formation of aquatic soils? Or is
> it only the terrestrial earthworms that do this and the aquatic plants
> mainly get the soils by erosion and sedimentation?

Aquatic soils (at least those I'm accustomed to stepping in) are never
stable long enough to have the long history of biological reprocessing
that creates terrestrial soils.  As a result, aquatic "soils" are not very
similar to terrestrial soils.  The ones I've looked closely at carry an
enormous biological load.  This goes way beyond worms.  Living organisms
of many types often comprise a significant part of the total bed volume. I
suspect that under stable, mid-season conditions that the soluble
macronutrient concentrations in most sediments are low and most of the
nutrients are locked up in and constantly cycled through the contained

Seasonal cycles cause large changes in the resident biota.  The dissolved
nutrients will increase after the population dies off and bacteria
mineralize the organic nutrients and decline again as the population
rebuilds.  This probably will lead to significant concentrations of
dissolved nutrients in the temperate spring and after periods when the
sediments are disturbed.

> Also somebody else said that aquatic mud was likely to be too high in
> macro nutrients. I'm not sure this is true either but would like to hear
> Dr Dave's comments. I think most sediment which travels down a river is
> getting pretty well leached although the mineral particles could still
> contain plenty of micro nutrients. We tend to think that lakes which are
> polluted with relatively high levels of nutrients are also going to have
> really rich sediments in the bottom. That may also not be true.

I think its real possible to collect an aquatic substrate and find it too
nutrient-rich to use in an aquarium.  The nutrient concentrations would be
low under undisturbed conditions, but when the substrate is moved to an
aquarium the death and decay of a large part of the resident biota would
cause high nutrient levels.

I've given thought to this problem for several years now and I don't think
you could use a "natural" aquatic substrate in an aquarium unless you paid
a great deal of attention to keeping the critters in the substrate alive
and working.  A possibly practical method of doing this would be to build
the soil up slowly over a period of months, starting from a mostly sterile

Roger Miller
Pepper the above with IMHOs, YMMV and so on, as you see fit.