Re: [APD] Re: High water evaporation

["S. Hieber" <shieber at yahoo_com>]

Thanks, K9,

But if you're replacing evaporated water, you don't need to
add more minerals just because you're adding more water.

Has anyone suggested using pure RO as the only source of
water for a fish or plant tank?  Or was the suggestion that
RO be used as top-off to replace evaported water?

I might have been reading poorly but I think the suggestion
was the latter.  In which case the point would be to *not*
add more minerals with the RO.

I read the original poster, who said "*like* laboratory
standard" [my emphasis] as speaking a bit loosely and not
trying to define standards for any particular laboratory.
And in most aquariums cases, it's like, you know, like good
enough ;-)  Unless there's some relatively high
concentrations of some things in the tap water that the RO
won't remove.  So, like, cut the poster some slack.  We
don't expect our RO to be perfect, why excpect the posts to
be?

Scott H.
--- K9AUB at aol_com wrote:
> >Some will disagree with me, but in theory, if you use
> reverse osmosis water
> >which is like laboratory standard of chemical purity.
> 
> Not even close.  Quality R/O membranes filter out about
> 95% of impurities 
> such as calcium, magnesium, carbonates, sulfates, etc. 
> The exact amount of 
> contaminants removed is going to depend on the type of
> membrane used and the number 
> of gallons it has filtered.  Removal of 90-95% of
> impurities would be 
> considered good performance for an R/O membrane, but
> would of course leave about 
> 5-10% of impurities behind.  For laboratory purity, you
> need to aggressively 
> filter water.  R/O followed by a high quality
> deionization column would produce 
> near laboratory standard water for most applications. 
> For absolute purity, the 
> "gold standard" is double distillation, which produces
> essentially 100% pure 
> water.  For aquarium use, such purity is wasted effort. 
> R/O water is certainly 
> pure enough for anything you're trying to accomplish, and
> would still require 
> minerals and fertilizers to be added if you want to use
> it for plants or fish. 
>  Running straight R/O water on fish is never a good idea.
>  They do need some 
> minerals in their water.


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