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Comparing fertiliser systems

Happy Thanksgiving to all the American list members.

Greg Moran wrote, during a discussion of the merits/demerits of gluconate vs
EDTA based Iron supplements:

> >No I don't think they _have_ to do that in order to decide they like our
> >product... I just meant that from a _scientific_ standpoint that
> is going
> >to be the most objective way for one to decide which is "best" for them.

To which Karen replied:

> I'm sure _you_ know that this wouldn't be a valid scientific test
> either...
> >From the minute the tanks are set up, they begin to diverge, and
> will never
> be "exactly" the same again.

I can understand the fact that every tank, once set up, becomes unique and
that there are many factors which contribute to it's health and condition. I
also understand the basic premise of the "scientific method" whereby only
one variable is changed in a properly designed experiment.

The product ranges we are dealing with here, from a number of different
manufacturers, are supposedly designed to provide all necessary plant
nutrients in a form and quantity required for good growth. Different
manufacturers choose to provide certain nutrients in various forms and
sometimes in different product types. For example, Dupla provides Potassium
in Duplaplant, their fertiliser tablets (info from the archives, from a
study conducted by George Booth several years ago), while Amano's ADA
products provide the same element in Brighty K, a water conditioner (from
their Web-site: Brighty K is specifically designed to provide for potassium
(K) supplementation and neutralising chlorine).

So, comparing one water conditioner to another as isolated products makes no
sense. Similar conclusions can probably be drawn for most individual
products, depending upon how much divergence there is between manufacturers
in deciding how to formulate their product lines.

But the product lines are designed and intended to be used in a
complimentary fashion - Dupla really recommends that you use their products
together to achieve maximum benefit, as does ADA and Seachem, Dennerele,
etc. Commercial considerations aside, this does tend to make sense -
especially so since we, as consumers, do not have access to independent and
unbiased chemical analysis of each product from each line. Isolated
instances exist where a hobbyist has had one or two products analysed and
has put the information online but nowhere have I seen a comprehensive
series of tests conducted on competing product lines. Lacking this physical
data, the only way we as aquarists can compare these different lines of
products is to use them (as they were designed) in actual aquariums.

If one tank is set up using Dupla's products and another is set up using,
for example, Aqualine Buschke products (substitute Amano, Seachem or any
other full-line range here, as you wish), and both tanks are maintained in
the same fashion and followed closely for a year, is there nothing of value
(scientific or otherwise) which can be drawn from a comparison of the two
systems at the end of that time?

Surely any gross deficiencies or excesses, if they exist, would become
visible within that time frame. Even with the unique nature of indivdual
tanks, if one product line failed to provide sufficient Magnesium
(substitute the essential element of your choice here) then over the course
of a year surely that deficiency would manifest itself in that particular
tank. I realise that diagnosing nutrient deficiencies can be problematic but
even if one was unable to pinpoint just exactly which nutrient was in short
supply (or excess, as the case may be), an observer would be able to say if
one product line was meeting the plant's needs as well as another product
line. At least for THAT particular aquarist, in THOSE particular tanks. And
would nothing be gained from such a study which could be of use to other
aquarists in THEIR tanks, under THEIR own unique circumstances?

Or are we forever doomed to be shooting in the dark and chanting the Dupla
mantra? (excuse me for that, I mean no disrespect for their products or for
anybody who uses them, as I have, happily, for several years).

Discussions of pKa's for different materials is fine for the technical, but
most list members are more practical than technical and a "practical"
comparison of one "system" to another "system" is surely more useful to us
as hobbyists. Several well respected list members have expressed (what seems
to me) scepticism over the validity (at least the scientific validity) of
such a test. Would anyone like to comment on HOW (or even IF) different
product lines can be compared in a manner which would meet the requirements
of "science" while at the same time be understandable and useful to us as


James Purchase
Toronto, Ontario
jpurch at interlog_com