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RE: Why doesn't anything live in substrate?

> Steve Lacy <slacy at wenet_net> wondered:
> > I've seen marine tanks where the substrate is alive with many types of 
> > worms and other goodies that digest waste, and keep the substrate
aerated 
> > and "alive."  When I ask my marine tank friends, they say that it "just 
> > happens" and they never added anything to their tank (other than live
rock)
> > 
> > I've never seen a freshwater tank with similar beasties.  Why not?

"James Purchase" <jpurch at interlog_com> responded:
> Actually, it doesn't really just happen. While _any_ substrate, fresh or
> marine, will, over time, become the home to a variety of microbes, "live
> sand" as the term is usually used, refers to a substrate that contains a
> wide variety of both microscopic and macroscopic life.

James is right, because most places other than Kansas has
discounted the theory of "abiogenesis",  where rats are created 
in a barn from nothing if you've left some oily rags there.  ;-))

(That was a cute joke relating to the Kansas Board of Education
decision on Darwinism a year ago... please feel free to flame me
offline if you're from Kansas.   ;-))))))))

I wanted to add one more thing, though:  There's a TON of stuff
suspended in marine systems (many kinds of salts, calcium, lots
of other compounds).  This makes the water more viscous (easier
to swim in the Mediterranean Ocean than Lake Michigan), and much
easier to support life (to a point, it's pretty salty in the Red Sea and
not a lot grows there.)  Haven't we all seen how much more viable
our freshwater snails and crustations are in a semi-brackish,
or harder-water environment?

Because of the additional compounds and additional environmental
diversity, it's much easier to sustain life and a much wider variety of 
life.  If for no other reason, a freshwater critter has to deal with the
osmotic gradient because impurities within the living system (inside
the critter's body) are much higher than impurities in fresh water.  
That's hard, in a physiological sense.  In the ocean, that's much 
less of an issue... a human's saline content (percentage) is actually 
about on par with the suspended salts in the ocean.

I've given this issue a lot of thought over the years, and I've concluded
that we CAN have things called "freshwater reefs", but they can't be
a flora/fauna match with marine reef systems.  In freshwater, we
are greatly blessed with plant diversity and greatly penalized with 
substrate-bound animals.  (For physiological reasons we can move
into next, plants typically can't handle salts and most animals tend 
to require salts.)

--charley
charleyb at cytomation_com