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Re: Osmocote experiments

>   As I write, I'm looking at a 20 High that I set up about 6-8 months
>ago. Last week I sold a Mermaid plant out of that tank and when I
>uprooted it, up came 3 beads. The beads are not much smaller than when I
>put them in there. Part of this reason COULD be because they might have
>swollen a bit. Anyway, this particular tank has no filter on it and the
>water is still clear. 

I have used Osmokote myself a few years ago... but did not follow up with
any intensive study or with as much intensity as you.  I have both buried it
in the substrate for underwater plants (a logical way to do it) and kept it
on top when growing emersed plants. What I remember noticing for the latter
was that the plastic capsules stayed intact, but lost their contents. If I
squeezed them, they collapsed. This suggests that their contents are water
soluble. I think I stopped using it for underwater substrates because I
think it contains sulfates.

>   Actually, uprooting these beads happens often and I have never tried
>to rebury them in the substrate. I mention this because I checked some
>other tanks where I know I have brought up many beads, yet I no longer
>see them. This might suggest they dissolve faster above the substrate or
>my eyesight isn't so hot.

 Please feel the beads in your underwater tank to see if they may be empty.

 I'll try to pay more attention to the  beads I
>just uncovered and see if I can see them disintegrate and over what
>period of time.
>   I suspect it would be easy enough to see how long they last in the
>substrate, if some were buried in the substrate against the front glass.

Yes and no, because of what I mentioned above. Unless the plastic dissolves,
the capsules will appear to still be there.

>   Also, I have been getting a lot of e-mail on how much Osmocote to use
>in the substrate. This has been a complete guess on my part, but the
>Osmocote comes with a little plastic spoon (looks to be about a tsp.). I
>have been using  about 1 level spoon per sq. ft.

You can estimate the amount of fertilizer in 1 level spoon by weighing its
contents and then running the calculations based on the % contents. I do not
have time at the moment, but I can do this when I get a change. This amount
can then be compared to a small piece (like 1/2 inch) of jobes plant stick
or plant tabs or other NPK fertilizers which I think would give similar
results). I  feel comfortable with the latter or even use of the osmokote
provided that they are used in SMALL quantities. 

I am still interested in getting a good way to judge the speed of time
release. Another method would be to test for nitrogen or phosphates using a
concentrated amount of the capsules in a small container of water. Here is
the experiment for someone to try:
a) bury some capsules under some sand under water, and in a separate
container b) place them in water. A small jar would be fine with a teaspoon
of capsules. Althought the concentrations are going to be higher than what
we want in an aquarium, they should be high enough to see quick results with
a test kit. The concentration can be tested on a daily basis and the change
in levels can be plotted over time. The amount of material used should not
be so much to cause the test kit to max out. i.e. they should allow the
concentrations to stay within the limits of the test kit (phosphates or
nitrates). Maybe the chemists can suggest the best indicator chemical that
won't undergo conversion after it is released. The test with the stuff
buried in the sand should show less concentration (or zero). 

I would like to see the experiment also done with eqivalent amount of plant
stick and plant tab for comparison. The entire thing could be over in 1 week
or may take longer. We just don't know. 

>   I would like to remind readers, that the criteria for my methods are
>normally based on cheap and easy, not maximum growth. Lastly, my methods
>come with no guarantee. 

Nicely put.
Neil Frank      Aquatic Gardeners Association         Raleigh, NC
      The Aquatic Gardener - journal of the AGA -  now in its seventh year!!