Hi all,
I have a similar jaundiced view to Clive on the honesty and integrity of many of the large suppliers of "specialist aquarium" equipment, fertilizers, fluorescent tubes and filter media.
I think in this case that they use ammonium polyphosphate for a reason, and that is because it is widely available and has properties as an emulsifier and chelating agent. If it was purely on a cost basis, urea (CO(NH2)2) would be cheaper.
My suspicion would be that the companies use what is the most cost effective option for them, which I can understand, but then they use advertising which is deliberately obscure and misleading (although presumably legal) to sell a, cheap to produce, product for a huge mark up.
I start from the premise that I'll review at the advertising blurb for the bits of science that I'm pretty sure that I understand.
Because I come from a scientific back-ground in botany and horticulture, and I've worked for ~20 years in a lab. where we did a lot of work in ecology and phytoremediation, I think I've probably got more understanding of the principles that under-pin much of what happens in the aquarium than the average fish keeper.
The other great advantage I have is that I work in the same school with statisticians, animal ecologists, plant physiologists, micro-biologists, plant ecologists and analytical chemists, so I when I don't understand something I can always ask a colleague.
For example when an analytical chemist with 35 years experience, in a lab. with ~£500,000's of pounds worth of kit, tells you it is quite difficult to measure some anions (like NO3-) accurately, you tend to take their word for it.
Whilst where on the subject of ions, plants can only take up nutrients when they are in solution as ions. Every NO3- or NH4+ ion is the same, it doesn't matter where it came from, it doesn't know it was from NH3NO3 or KNO3 etc., once they are in solution they are all the same.
Reactive elements like potassium (K), nitrogen (N) and oxygen (O) have been on Earth for the last 4.5 billion years combined in a huge range of compounds, they don't "know" what those compunds were.
It is the same with fluorescent tubes with "special phosphors" etc. It is all smoke and mirrors, or the Emperor's new clothes.
cheers Darrel