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Re: Clay balls or pellets in an all gravel substrate

A few days ago, Bill Terburg wrote:
>Recently there has been some discussion by Steve Pushak and George
>Booth on the subject of the use of clay balls and or pellets.   

Recently and then some <g>.

>In our experience we've found that clay pellets
>composed of one or two parts clay to one part pmdd dry mix works
>extremely well as a general fertilizer and controled substrate
>additive.  In our experience we've found that it works better than
>layered substrates of clay, laterite etc.  We think that the reason may
>be that it offers better control of conditions than other approaches. 
>We never use anything other than gravel anymore, and we have fantastic

I guess I have to take issue with some of that, depending on the exact
meaning intended. I will address my comments as if Bill was comparing
gravel plus clay balls to a Dupla substrate. For reference, a Dupla
substrare is a small amount of Duplarit-G (granular laterite from Sri
Lanka) mixed into the lower 1/3 of the otherwise plain gravel substrate,
which could be construed as "layering". Substrate heating coils are part of
this, of course.    

>Water flows slowly through these
>habitats in two main ways, through stream flow, and by percolation.  
>The effects of stream flow in the aquarium can be accomplished by
>periodic or continual water changing.  The effects of natural 
>percolation however are extremely hard to achieve.   

A working hypothesis is that the heating coils achieve exactly that. Not
difficult at all. 

>When water
>naturally percolates through stream or pond bottoms the concentration of
>nutrients increases in the bottom soils and decreases in the free water
>around the plants.  Rooted plants thrive while primitive plants (algae)
>are deprived and are thereby controlled.   

Yes, the coils set up convection currents that bring nutrients into the
substrate where they are captured by negative binding sites. 

>Nutrients do not move naturally from
>the free water into the substrate, but rather move un-naturally from the
>substrate into the free water.  

Not in the Dupla substrate case. 

>Only with the greatest of good fortune
>and or skill can one set up a layered high nutrient substrate without
>having some significant control problems.  

Yes, diregarding the unnecessary "high nutrient" part, one is fortunate
indeed if one has heard of Dupla and even more fortunate if one has enough
skill to fork over bucks for the equipment. Oops, my cynicism is showing.  

>Some folks even install
>heaters to get the "action" really cooking.  We never heat our gravel

Mere heat will not get the job done, as has been debated here in the past
and will be again in the future. 

>We believe that the most prudent approach is to add clay/fertilizer
>balls or pellets sparingly underneath individual plants, so that there
>is never enough of this material that it can get "out of control".  

This would be wonderful if the plants don't grow enough to require periodic
uprooting, pruning and replanting (is this, indeed, the case?). However,
once the plant roots have grown fond of their personal clay ball, and have
embedded themselves into it, will not the act of uprooting also pull up the
clay ball and dispserse the contents into the water column? Even if that
were not true, would one not have trouble replanting the plant in just the
right spot to take advantage of the clay ball?  This seems very restrictive
and would discourage free-wheeling aquascaping attempts. 
>We have performed an experiment wherein we added
>an amount of fertilizer in pellet form to the substrate which if added
>directly to the free water would have registered significantly on our
>test kits.  But yet a day later, 2,3,4,5,7, still no reading.

And have you checked to see if any of the fertilizer is getting out of the
clay ball AT ALL? If not, you might was well put the fertlizer in ping-pong

>In another experiment, 
>fertilizer/clay pellets were placed into test tubes with a 1" layer of
>gravel below and 1" layer above.  Within a day the clay pellets had
>disolved and settled through the gravel to the bottom of each tube, no
>matter how fine the gravel was.  

That seems like mighty fast dissolving and is contrary to observations made
by other aquarists using clay balls, including myself (Duplarit-K in an UGF

>We've observed the same thing in
>planted tanks.   This action  sets up a very fine layer of fertilized
>clay at the bottom of the tank which seems to be a more controllable
>situation than a massive laterite or clay layer.   

This very same thing is seen to occur in a Dupla substrate, which, by the
way, does not fit the term "massive laterite layer". If one needs to tear
down the tank (not due to an exhausted substrate, but perhaops due to
remodeling the house, retirement, etc), one finds a very thin layer of pure
laterite at the very bottom, with smaller amounts in the original lower 1/3. 
Did I miss the part where you have to add new clay pellets at reqular
intervals?  What other additions are needed? The clay balls (like Pushacks)
are not a complete fertilizer. Do you have details of the complete regimen
you are promoting? 

George Booth, Ft. Collins, Colorado (booth at frii_com)
  Back on-line! New URL! Slightly new look! Same good data!