Re: Subject: UG heating coils & RUG filters

>  - Steve wrote:
> Here's my concept: what if we take some 1-2" dia PVC tubing and fill it with
> sand, organic material and laterite (or other iron rich clay) and place it in
> the corner or bottom or even OUTSIDE the tank and allow water to leach through
> this into the substrate. The substrate can be a mixture of vermiculite, sand or
> fine gravel over a conventional UG filter plate or tubes. The outflow from the 
> leaching column could be directed under the substrate and provide circulation
> to the substrate. Since much less organic material would be found in the
> substrate, the problem of H2S formation should be much less! The organic
> material could be humus, compost, peat or regular dirt. This would provide 
> humic acid which should be able to reduce some of the iron compounds. The 
> factors which require tuning are:
> a) organic material b) % composition c) flow rate d) temperature? pH?

Hmmm.  I think I like this...?

Can we use the sand (or whatever) inside the tube PRIMARILY to slow the water
rate to the substrate from a power head for slow flow rates?  Or are we just
fighting ourselves?  Of course, sand compacts over time (if not mixed as you
suggest with peat, laterite, etc).  Maybe we could look at vermiculite for 
the fill.  Although it's a ?silicate clay, I don't think it compacts much 
over time because it's so porous.  OTOH, because the roots will never reach 
the vermiculite (and hence the CE sites), ?much of the supplements we add 
may be bound in the substrate tubing away from the plants.  Maybe mine's a bad
idea, or could this merely be a buffer for slow leaching into the substrate 

Do we really need the organic material if we're adding iron supplements right
to the substrate?  I know lowering the pH may increase the available iron,
but what if our supplements are already in available forms (Dupla drops)?   If 
the substrate has a lot of CEC and we add directly to the substrate, I'm hoping 
the iron goes right to binding on an exchange site.  (I just seem to have a 
hard time adding soil/peat to the bottom of my aquarium, even though I know 
this is what nature provides.  I'm nervous about 
disease/mess/maintenence/decomposition in this "clean" hydroponic environment, 
and I know that carbon-based wastes will build up over time anyway.)

Finally, I've come full circle and am now wondering why I hate RUGF/UGF so
much.  In slow flow rates, it seems to be the only (real) alternative to
heat coils for keeping a 4" substrate from going anaerobic.  

>>>   Is this true?   <<<

Partially because of heat coils/laterite cost, I think I'm leaning towards 
some of David Webb's ideas that allow for RUGF from PVC with (automated) 
debris removal, slow flow rates, and access directly to the substrate for 
iron additives.

                   (I made a rhyme!) 
                 The Substrate Limerick
            Slow circulation is provided by coils,
            and without O2 the substrate spoils. 
            But how low with the flow--
            can we really go?
            So we watch as our aquarium boils.   :-)

Please don't take offense at my slander to your $864 laterite/heat coil
substrate!  This is my sour grapes because I can't afford to do that
also!  :-) :-)

cbay at lookout_ecte.uswc.uswest.com