First posting and interesting question

Hello everyone,

     As my header states this is my first post to this mail list, and as such
I feel the need to ask a question that might raise some discussion.  Why the
great need for water change?  ( I am 22, and had keep fish when I was
younger, when the idea of water change was unspoken)  It is my understanding
that water changes are used to remove harmful toxins (ammonia, nitrites, and
nitrates) that may effect fish health (and to replace trace minerals, for us
plant-people)  Recently, I have been researching into the inner workings of
saltwater reef aquariums.  As many know, reef aquariums use Live Rock to
convert ammonia and nitrites into nitrates and then consume the nitrates
(thereby keeping very-very low levels of all three substances)  In the
well-planted tank, similar processes are occuring (I won't go into this,
because we all probably know it already)  If trace elements are replaced, I
see no reason to change water so frequently.
I am not suggesting no water changes, just reduced changes.  Of course, I
believe this could only apply to moderate to well-planted aquariums.  I'm
sure there are so holes in this theory, but hopeful we can discuss it futher.

     - Keith