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Re: Plant nutrients in water column

Karen wrote:

> Steve P. quoted Dr. Dave as saying:
> > I
> >asked the same type of question in a paper published in 1982 and came up
> >with the same result (Huebert and Gorham (Aquatic Bot. 16: 269 to 283).
> >These experiments, and several others, indicated that with a fertile
> >substrate the only nutrients required in the water column are Ca, Mg, K
> >and of course CO2 (I must admit, though, that the evidence for
> >micronutrients is scant and it is in fact likely that water column
> >additions of micronutrients is a good strategy ... though my swords and
> >Sagittaria are completely indifferent to whether or not I add
> >micronutrients)
> Of course, this makes the supposition that the aquarist is _only_
> interested in growing root feeding plants who's roots are IN the substrate.
>  Just making it clear that this strategy will not work for those plants who
> depend on the water column for all nutrients.

If we could eliminate all source of nutrients in the water, that would
be true. I have found that if I don't make micro nutrient additions,
that there does _seem_ to be a shortage of Fe in the water. Salvinia and
algae seem to be inhibited by this. I have some Ceratopteris
thalictroides in my 75 gallon tank which is currently doing very well. I
confess to adding a dose of micro nutrients two weeks ago to see if it
would alter any growth rates or the size of my R macrandra leaves which
I would like to see larger. (no change) I suspect that the Rotala would
benefit by addition of more substrate nutrients such as P and N. I have
not added any clay balls to these fellows.

I use floating plants in the large tanks occasionally as nutrient
sponges, so if they do not grow rapidly, I'm not offended. Java fern
doesn't really have roots either but it also seems to grow quite well in
my tanks. It might grow faster with more water fertilization, I don't

Steve Pushak                              Vancouver, BC, CANADA 

Visit "Steve's Aquatic Page"      http://home.infinet.net/teban/
 for LOTS of pics, tips and links for aquatic gardening!!!