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Re: using plant spikes

On Sun, 2 Jan 2000, Bob Delon asked whether he could use Jobes spikes
other than the fern and palm variety, and how much to use.

You can use them in your tank.  The fern and palm spikes are 16-2-6, so
you have some other kind.  I've used the house plant formulation in my
tanks before without ill effects.

I cut the sticks into quarters - sometimes eighths - and push them into
the substrate around plants that seem to need it.  I usually use one piece
for smaller plants or small groups of stems and two for larger plants and
heavy-feeding plants like big Echinodorus.  When you fertilize this way
you aren't fertilizing the tank as a whole, just the plants you treat, so
I don't think there's a formula for sticks/gallon.  I have never
fertilized all the plants in a tank at the same time (after all, different
plants have different needs) and I don't think I've ever placed more than
three sticks in my 55 gallon tank at any one time and never more than two
in any of my smaller tanks.

You might need some kind of sticks/gallon rule if you force substrate
circulation with a UGF, RUGF or (maybe) substrate heating.  Without forced
circulation the nutrients are mostly limited to the substrate because the
rate of diffusion out of the substrate is fairly slow.  I also bank on
Karen Randall's argument that if plants move water from their roots to the
leaves then they also cause a downward movement of water through the
substrate to the roots.  That helps aerate the substrate; it also helps
keep substrate nutrients out of the water column.

There is some direct evidence that aquatic plants do move water from roots
to shoots.  There is also a wealth of indirect evidence; aquatic plants
are known to translocate nutrients from their roots to their leaves, which
I think they would do by moving the water that contains the nutrients.

I speculate that root feeding this way promotes flow of water downward
through the substrate.  Plants can take up nutrients from either their
leaves or their roots.  If the plants get most of their nutrients by
foliar uptake from the water column then there should be little flow from
roots to shoots.  But, if nutrients are consistently provided in the
substrate, then the nutrient levels in the water column will be low and
the plants will adjust to get most of their nutrients through a relatively
strong flow of water from roots to shoots.  The strong flow will keep
fertilizers placed in the substrate from leaking back into the water

Roger Miller