[APD] Re: Peat with wetting agent

[Michi Henning <michi at triodia_com>]

> I called the company and they said the wetting agent was a surfactant
> that did not have a common name and could not say if it was good
> or bad to use it in the aquarium.

Wetting agents reduce surface tension of the water. They typically
contain anionic tensides, which are molecules that have a water-loving
(hydrophilic) end, and a water-repellent (hydrophobic) end. Common
soap is a typical wetting agent, but there are many organic molecules
that meet this description (many aromatic hydrocarbons, for example,
many of which are known to be carcinogenic or toxic).

Many wetting agents also contain nonionic tensides, which help to clump
fatty parts into a gel. Phosphoric acid and 2-ethylhexyl ester are
nonionic tensides.

So, without knowing exactly what is in your specific mixture, you may
end up with anything from no problem at all to massive toxicity.
I'd be inclined not to risk it.

> Can this be safely used under my flourite when I set up a new
> planted tank?

In general, I would advise against combining peat and Flourite or
laterite in the substrate. I made that mistake once myself. Initially,
things went extremely well and the plants were growing beautifully.
But after a few months, I ran into massive problems with algae growth,
especially green water. All the usual tests (pH, KH, GH, CO2, O2, PO4,
NH4, NO2, NO3) were fine. Eventually, I tested for silicates and found
that they were completely through the roof, well above the maximum 
reading of the test kit (at least 100ppm), despite the fact that my
tap water contains almost no silicates.

The only possible source was the substrate: laterite and Flourite
quite a lot of aluminium silicate. The peat in the substrate creates
a strongly acidic environment, which causes the aluminium silicate
to dissociate, and you end up with tons of silicates in the water
column. In turn, diatoms build their skeleton out of silicates, so
I suspect that the silicates were to blame for my ongoing problems.
In the end, I emptied the tank, replaced the substrate with a gravel
and Fluorite mixture, and haven't had any problems since.

So, I'd be cautios about mixing peat and Fluorite. Use one or the other,
but not both.

Cheers,

Michi.




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