[APD] Re: High water evaporation in a planted aquarium

["Robert T Ricketts" <rtricketts at erols_com>]

Mark BoolyBooly wrote:
>Some will disagree with me, but in theory, if you use reverse osmosis water
>which is like laboratory standard of chemical purity, then you can keep a
>tank on good order by adding water and separately add trace elements and
>essential minerals to it and not taking away anything except for excess
>vegetation.

I'm one of the ones who will disagree.  RO may be a lab standard, but RO,
like tap, is not a single purity standard.  It depends on the operation of
the membranes and the rejection rate.  The "purity" (poor term in practice)
is defined solely by the resistance/conductivity/TDS of the output water.
The fact that it has been through an RO unit does not in itself define the
purity at all.  If you wanted the closest you can get to "pure" water, you
would want WFI (water for injection), which itself is prepared from high
resistance RODI.  But that would be a complete waste for tank use IMHO, and
astronomically expensive.  The color of the water in a white bucket has not
been determined either - because the bucket would contaminate the water.

There are some other assumptions behind the statement that should be
considered as well.  The first was discussed in the first paragraph.  The
next assumption would be that the hobbyist never ever put in more
fertilizer/supplement than the plants would uptake, and that the livestock
in the tank never ever contributed anything to the water which the plants
could not and would not uptake (anyone know of aquarium plants which use
phenols?), nor would such materials ever be added with feeding.  Without
absurdities such as full spectrophotometer and flame photometer analyses,
followed by literature searches to find any negatives associated with the
materials identified, you will never know beyond the crudity of hobby tests.
Even Diana Waldstad does some water changes, although at very long
intervals.  A closed ecosystem has not yet been done successfully for
indefinite operation, and an aquarium with routine supplementation and
feeding of livestock is far from a closed system.

I personally can find no valid basis for operating tanks without regular and
significant water changes, in part for the reasons Tom Barr has presented so
many times on this list, and in part for removal/reduction/dilution of all
the undetected materials added to or produced in the tank biologically.
Others may do as they will, but I hope that they do so with knowledge and
acceptance of their own assumptions.

Robert

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