Tetra plant products (was The FAQ)

In Aquatic Plants Digest V2 #4, Stephen.Pushak at saudan_HAC.COM wrote:

>My feeling is that we could
>come up with a list of good (or excellent) fertilizers and a list
>of those which are just a waste of money (like the Tetra products
>(hope I don't upset any loyal Tetra fertilizer advocates ;-))

I'm just curious as to why the Tetra products are considered a waste of
money? My admittedly lo-tech plant tank (loam/vermiculite substrate under
aquarium gravel, yeast CO2), seems to do well with them. At least the
Hygrophilia thinks so! I use FloraPride and the Crypto-Dunger tabs.

I haven't seen the Tetra products mentioned on the list, what with all the
talk of the Dupla products, and the advanced chemistry discussions. Which I
enjoy, and someday, the chemistry will filter its way through all the other
stuff in my brain (like Star Trek trivia and Saab spark plug part #s  8-).

All I want to know, is, am I poisoning my plants and/or fish by using this
stuff, or is it just that there are different and/or better products out

I'm not averse to changing, I'm just searching for knowledge.