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Re: Floride in tap water

> Date: Mon, 26 Jun 2000 23:05:15 +1000
> From: "Neil Travis" <travisn at gravity_net.au>
> Subject: Re:Re: Floride in tap water (wasAPD V4 #364
> well looks like I have made a partial blunder. I was confusing Fluoride with
> Chlorine.

Fluoride ions are barely distinguishable from chloride ions -- that is,
non-toxic in the extreme. Fluorine and chlorine are both very aggressive
elements that are quite toxic.

> As with fluoride it is a very stable chemical but also is very subseptible
> to auto chelation with other minerals in the water. Eg if you have clay that
> is high in Aluminium then kiss your fluoride goodbye.Most other metals
> produce simular results.

Clay contains alumina or aluminum silicate, both highly stable and unlikely
to react much with fluoride ions. It contains no free aluminum. The fluoride
ion's ability to react with tooth enamel (a calcium compound) is why it is a
decay preventive, so some tiny amount is possibly attached to clay
particles, too.

> The end result being that we in the planted aquaria hobby add so much extra
> minerals to our water that  they in effect combine with the fluoride and
> convert it to insoluble forms. This info was supplied by a Geo Chemist at
> Melbourne Water but the disturbing factor is after a few years how much of
> this insoluble muck builds up in the fish tank as it never dissipates.

None, if you are doing regular water changes. Look at the amounts. The
substrate sees many times as much chloride, and that doesn't build up

> On the good side at least for fish breeding the initial proportion is
> minimal but is acknowledged as harmful to fish eggs in the fact that it can
> harden the egg shells and prevent the fish from breaking free. Should this
> occur I was advised that distilled water is the best option for hatching the
> eggs 1st

The trace amounts of sodium fluoride used for dental protection in tap water
are most unlikely to have any such effect on eggs, any more than sodium
chloride does in tiny amounts (the two are almost identical, chemically). 

The eggs are incredibly more sensitive to the total dissolved solids (no
matter almost what they are), for the osmotic pressure across the outer
membrane must be maintained. In some hard-water species, distilled water
will burst the eggs long before they are ready to hatch. In others, it may
build internal pressure that eases the hatch. No generalization is safe,
here, IMHO.


Wright Huntley, Fremont CA, USA, 510 494-8679  huntleyone at home dot com

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