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Plant nutrients in water column

Steve P. wrote:

>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 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

It depends on what plants you enjoy working with, and what your goals are
for them.  If you use floaters or water column feeders strictly as nutrient
sponges, you don't really care if they die out, or are at least greatly
reduced in size or number.  If you are purposely growing these plants for
their own sake, and have a good number of them in the tank, you might find
that they can quite quickly exhaust the nutrients available in the water
column given good light and supplemental CO2, even with nutrients leaching
from a soil substrate.  I saw strong evidence of this in plants grown by
Dorothy Reimer in her soil based tanks.  

Neil could tell us if he has had the same experience.  

>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.

It has been my experience that this plant is a much stronger root feeder
than one might expect.  It is one of the few plants that I _always_ grow in
soil. (in a pot :-)

Karen Randall
Aquatic Gardeners Association