Re: substrate clay balls

> From: Michael Eckardt <mike at odg_com>
> What do you think of the following to rejuvenate a rather sterile substrate
> (with thanks to Manfred Wirz, who came up with the idea of clay balls):

Good article but it needs a summary. Guess this is it. :-)

> - - take clean, dry clay and mix it with Dupla24 drops until it becomes
> like playdough,

As an alternative, you could mix in super-fine steel wool preferably 
after it has rusted for several weeks. It could be that unoxidized
Fe will dissolve as Fe++ more easily than from the reduction of ferric
oxide so there _might_ be an advantage in used un-rusted steel wool. 
[Question for the chemists]
Or will it stay undissolved as metallic Fe in a reducing environment?
Or could it result in too much Fe++?

> - - roll 1/2" balls, punch a hole into them and add some hydroponic 
> fertilizer (NPK + micronutrients)

My thought was to use the slow-release NPK fertilizer pellets. Anything 
to delay the release of nutrients and prolong the fertility of the
substrate. Another alternative is mixing peat with the clay. Less
problem with an unwanted burst of nutrients if you disturb a soft
clay ball later. The theory is that peat decays very slowly,
gradually releasing nutrients.

> My thought
> - - close the hole again by rolling the balls once more and put them into
> a microwave oven (on very low) for a minute or until dry and hard,

I'd plan to make lots of em in advance and so they could just dry
hard in sunlight or wherever.

> - - then push the clay balls into the substrate near plants that 
> need a little boost.
> To me, it seems the clay locks in the fertilizer both physically 
> and chemically
> and only plant roots can easily get at them.

Yes, my understanding is that the fine clay particles actually
form a type of chemical bond as they dry and this will really
limit diffusion. Paul suggested a similar idea in letting a layer
of clay or mud dry to a hard layer in the empty aquarium before
covering with fine sand and planting.

I'd strongly recommend using potter's clay since it is very fine
and contains no sand. It's very, very hard to find clay sediment
that isn't contaminated with sand. You can extract it (kinda fun)
but its more work than the cost of potter's clay is worth.

> The fact the the iron may be oxidized is fine because deep in the substrate
> the Fe3+ will be reduced again anyhow.

We need some experiments to establish how much Fe could be made
available by these various methods. Too much could have undesirable
effects too couldn't it such as blocking uptake of other nutrients?

> My Crypt. wendtii's are growing hairroots _out_ of the substrate, 
> straight up into the water column.
> Why would that be? The plants are very healthy otherwise.

Have you disturbed them so that the roots became exposed? The only
time I have seen C wendtii emerge (aside from being disturbed) is
to push a new leaf stem out. Could you have aggressive fish?
Crypts seem to love to have their roots in the soil if there is
any in the substrate. I'm preparing some Paul K style substrates in
small containers/tanks for experimentation. More later...

One point, it seems like it might be a good idea to mix your
potting soil, top-soil or earthworm casting soil with water
and strain the slurry through a screen or sieve. There was a LOT
of fibrous woody material in the large bag of earthworm soil I
bought on the weekend. For a general substrate, I don't think
you want those bits of wood & fiber in there; too much potential 
for relatively fast decay (as opposed to peat). It could be that
the stuff is mixed with sphagnum peat moss and it never got all
the way composted. It could have been allright for swords or
Crypts but...

I threw the fiberous stuff into my soil compost tub. Its great
for house plants and with time and composting, aquarium plants

Once you have the mushy mud, you have to let the water seep out
of it and preferably dry it in a layer in the bottom of the
aquarium. A lot of the water will come to the top if you let
it sit for a few minutes or hours. Save that water; it's great
for adding in small amounts for your house plants or as a 
nutrient supplement for aquatic plants. Paul K has a formula
for calculating the potency but I don't have his article in
TAG for reference. Paul calculates things in weird units 
called Hoaglands ;-) but we need something universal like
tsps per gal (per watt?) per specific gravity.

Steve in drizzly Vancouver