Re: Aquatic Plants Digest V1 #104

On Sun, 4 Jun 1995 03:39:01 -0400 you wrote:
>whether it would work to buy plain undyed modeling
>clay and some ferric sulfate, mix the ferric sulfate in the clay, form
>it into little balls, let it dry, then plug them into the substrate?
>Steve Black
>blacks at rosnet_strose.edu

Steve, it is my understanding that the ferric form (Fe+++) is less
useful to the plants than the more reduced ferrous form (Fe++).  If
this is backwards, someone please correct me.

In addition, both sulfates are soluble, so the first thing that would
happen would be that the iron salts would dissolve and float thru the
tanks water.  The next thing would depend on what substrates you had
available for the iron ions to adsorb to (assuming that you did NOT
have a anion available to form an insoluble compound).  If you had
some high CAC substance in the substrate and its sites were not
already occupied by something with a higher affinity for the sites
than iron, the iron would adsorb there, releasing what had been there
before.  If you had vermiculite in the substrate, it might adsorb the
iron.  From what I understand, when the plant wants iron, it secretes
acid from its roots, hope to displace an iron with H+.  

Hey you chemists, is that it?   Dave
Dave Gomberg, Experimenta      San Francisco CA      gomberg at wcf_com