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Re: cables from the UK

> Date: Mon, 02 Jun 2003 13:10:52 -0400
> From: Thomas Barr <tcbiii at earthlink_net>

> Copied from George (where is he anyway?:-):

Still right here in the boonies of Colorado,  dodging the quarterly layoffs
(so far).

> First off Dupla Cables have very good suction cups and stay in place
> than any cables I've ever seen or used.

It should be pointed out in all honesty that the very expensive cable
holders/suction cups are only useful when first installing the cables. Once
the gravel is properly laid, the cable holders are pretty redundant.  And
after a few monster sword plant removals, quite a few of the cable holders
go into the spare parts bin.  But they make for a pretty cool picture
sittin' in the bare tank before they are covered up.  See the on-line
Aquascaping seminar on my website for said cool pictures.

Tom did a great job of refuting the points I made. I guess I now need to
refute some of the refutals.

Keep in mind two things:

1) I believe that Dupla did due diligence when they worked out the concept
of the heating coils. They didn't do a good job of writing about the whys
and wherefores and the science thereof, but I believe they were NOT out to
just sell some fancy gizmos to the bozos to make a few bucks.

B) I experiemented with lots of setups during the Early Years (1986 to
1995).  I became convinced in my own mind that coils did the job for us. Our
non-coil setups did OK for awhile then went downhill. Coil setups never did
(to this day).

So, based on 1) and B) and many readings of The Optimum Aquarium, I
postulated the 6 points that Andrew McLeod was so kind to quote in his
posting. These points were discussed during a panel session at the first AGA
conference and I think the panel was not unkind to the concept of heating
coils. They didn't run out and buy coils, mind you, but they didn't do a
dog-pile on George, either.

So, here's a couple of refutes. Keep in mind this is all conjecture (on both
sides of the argument) so it's a great
how-many-angelfish-can-dance-on-the-head-of-a-pin discussion.

> > 1) Provide warmth in the substrate for certain plant species (Barclaya
> > longifolia, specifically).  In this case the substrate should be warmer
> > than the water.
> Why? In nature the substrate is often the coolest part. ... The source of
heat in natural systems is the sun.

The cables are supposed to mimic warm groundwater rising through the
substrate bed; warm mineral springs, that kind of thing. Sure, not ALL
ecosystems are like this, but maybe some places have warm groundwater
seeping UP from below the substrate.  The sun is not directly involved in
this - consider magma (magna?) near the surface.

> The notion that this is something based off nature that can be generalized
> and a natural processes is a big stretch. Nature has many different
> environments that aquatic plants live and thrive it.

Yes and this is one of them. We can't begin to emulate nature in our little
glass boxes. Dupla has attempted to recreate once aspect of this with
heating coils.

> > 2) Provide warmth in the substrate to speed up biochemical
> > processes.
> Well, here's the main thing. But this assumes that you need sped up
> biochemical processes at all.

It might be good to match high-light/high-CO2 with high-speed biochemical
processes.  Or med-light/med-CO2 with slightly greater bio-chem processes.
All things in balance, right?

> Roots don't just sit there, they are not passive.
> They are active and pump O2 and H+ down into the root zone.

>From my understanding, the H+ ions that the roots pump down are exchanged
for nutrient ions during adsorption from the chelated ions in the substrate.
Otherwise, what a waste of good H+.

> Adding heat another 1 cm deeper on the outside of glass will not change
> anything significant for anyone to ever worry about.
> I stand by the reptile pads if someone wants to try it out for themselves
> and it will not cost much/nor cause you to uproot a tank, it's easy to

Nah, I think reptile pads and other low density heat sources are only good
for a couple of the 6 points. I doubt they would create any useful
convection currents.

> > 3) Transport nutrients from the water into the substrate.
> Use root tabs/laterite etc if you feel this is needed.

Bah. Holy clay balls, Batman. Why spend the time sticking fertilizers into
the substrate when the coils can move them in "automatically".  You add
nutrients to the water column already. Why not let them also be moved into
and used in the substrate by heavy root feeders?

> NH4 should be removed quickly by the leaves, not the roots.

I think NH4 is just as available to be pulled into the substrate as it is to
be taken up by leaves. The implication here is that the leaves are somehow
NH4 magnets and the stuff just gets sucked in as fast as it is produced.
This would also imply that there is NO biological filtration in a planted
tank since there will be NO NH4 for the bacteria to feed on. I find that a
little hard to swallow.

> Some build up,and breakdown of organic matter eventually works it's way
> into the substrate but the flows in/out of the substrate are TOO fast to
> maintain a better reductive environment than no flow at all.

No one has ever quantified the amount of flow produced by coils. Arguments
of "too fast" or "too slow" can't be used succesfully.

> Diffusion alone is enough to have an optimum flow rate in/out of a
> substrate. Tropica agrees and their case study tank showed that cables
> provided too much flow.

Have they published data on this?  I would love to see it. How was "too much
flow" determined?  I had pretty good luck with an UGF tank and that sure had
a lot more flow than cables ever would create.

> Well why add iron to the substrate then?

Iron gets used up and needs to be replaced. Either by sticking fresh stuff
into the subtrate or by  convenient convection currents.

> > This
> > will replenish nutrients used by the roots and provide long
> > term viability (in terms of years).
> My tanks and plants are quite viable, I don't use cable or pads these

My tanks weren't. You sea level guys sure are lucky <g>.

> 4) Transport harmful products out of
> > the substrate.  Decomposition products may be harmful to plant roots.
> There's plenty of flow to remove anything w/o cables.

Why isn't yucky hydrogen sulfide removed the same way?  How does this
explain the terrors of Anaerobic Substrate.

> > There is also conjecture
> > that plants give of low level toxins to keep other plants out of their
> > territory (successful weeds have made this an art form).
> Show me one submerged aquatic that does this. Aquatic plants have little
> reason/advantage in doing so.

Gosh, isn't this how weeds work?  Are there no aquatic weeds?  Don't some
non-native species somehow choke out poor little native plants? Is this just
by being a really fast grower?

> > If these toxins
> > build up due to poor circulation, the plant may
> > harm itself.
> I don't buy this idea one bit. Diffusion is plenty fast enough to bring
> out of the substrate. Water changes provide plenty of export for any
> "toxins". And what about non Carbon enriched tanks? I don't change the
> for months on end, the most plants don't harm themselves there.

How about "years on end"?

> > 5) Provide a chelating medium that binds the divalent state
> > of trace
> > elements with an organic molecule, enabling the trace element to be
> > adsorbed by root hairs.
> We can and do use a number of chelators. Plants can also use rust and
> the iron to take it in. Folks can use iron filings, rust etc to add iron
> gravel if they want. I've done it.
> You can add peat also. Chelates, reduces etc and provides a good source of
> organic matter till the tank matures well on its own.

OK, so I guess point 5 is well taken.

> > 6) Provide a reducing rather than oxidizing
> > environment so that trace elements are kept in their divalent state
> > by plants) or
> > are reduced from their oxidized trivalent state.  Iron especially will
> > rapidly oxidize in water with normal levels of oxygen.
> So lowering the flow rate would help, cables provide too much flow rate.

Bah, humbug. Give me numbers!

> Where is George? He better come to Dallas for this year's AGA meeting!

Well, that's up to Karla!

> Regards,
> Tom Barr


George Booth in Ft. Collins, CO (gbooth at frii dot com)
  The website for Aquatic Gardeners by Aquatic Gardeners
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