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Re: Cables, the debate
- To: <Aquatic-Plants at actwin_com>
- Subject: Re: Cables, the debate
- From: Thomas Barr <tcbiii at earthlink_net>
- Date: Tue, 03 Jun 2003 12:19:42 -0400
- In-reply-to: <200306031138.h53BcV3O021388@otter.actwin.com>
- User-agent: Microsoft-Outlook-Express-Macintosh-Edition/5.02.2022
>> Copied from George (where is he anyway?:-):
> Still right here in the boonies of Colorado, dodging the quarterly layoffs
> (so far).
Well... finally flushed him out of lurk mode:-)
> 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).
I think a good deal of this was due to the macro and other issues that might
have cause tank decline or the infamous tank "stall".
Fresh tanks often have enough nutrients or the owner tends to feeding or
whatever source of the nutrients maybe and stops the routine etc.
>>> 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.
Humm, I know of a spring here in Florida called Warm mineral springs(Warm
hardwater/high CO2), they have a few plants but they don't grow where the
water perculates up through the substrate. They did find some 12,000yo Human
Indian and saber tooth bones/remains. It's a neat spring, deep, good for
scuba, bad for plants. Water is fairly warm vs the average spring here.
Some springs go very deep here and some also in other regions do go very
> 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.
Really? How much magma would I dose?:-)
I'm using Florida as an example since it has year round plants, 100'S of
springs with brackish, fresh water w/soft, medium and hardness, sulfur,
warm, most are around 68-73F year round, no variation to speak of
temperature/chemical wise. This makes them ideal natural experiment
But in the winter, the spring is warm compared to the surrounding air but
the water temp stays very constant regardless.
This is one reason I want folks to come here to see all the variation in
habitat and wonder why this might be. 8000 lakes, many rivers/streams.
Most with plants, no winter ice etc.
>> 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+.
But this exchange causes enough flow on it's own along with the plant
creating it's proper root environment. Plain old Diffusion exchanges enough
flow for optimal root/plant growth on it's own. Cables/coils causes too much
>> 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.
But _how much_ current is needed and is -this_ what improves plant growth?
Or is it something else? I've used my RFUG's for currents in the substrates,
I could use much of this argument using these as an example. Their flow can
be varied. Adding heat(Rather than simply equilibrating the heat) is the
only thing they don't do. They can have their flow rates varied and
manipulated over a wide range and this can be _measured_ relatively easily.
Cables can also but it/'s a fair amount of trouble for any hobbyist if not
impossible for them.
>>> 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?
RFUG and diffusion alone should be able to do this. Detritus can work it's
way down there in either system.
It's all a question of warmth(speeds up bacteria etc but __also___ root
metabolism) and how fast the flow rate through the substrate is.
I think the warmth idea with speeding up root metabolism is something to
think about when considering why cable might work.
Maybe Dupla's idea was:
Keeping the water cooler above allows for more O2/CO2 in the water, slower
algae/plant growth and allows the roots to provide an amplified source of
nutrients and growth.
>> 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.
Well it's got to get down there before the leaves have a chance to take it
in and the filter's bacteria convert it. It takes too much time for this to
occur and the reductive environment need to preserve the NH4 without those
pesky bacteria converting it is reduced by the increased flow rates
associated with cables. A simple sub with no flow except diffusion will
retain the NH4 better that manages to get down there.
> The implication here is that the leaves are somehow
> NH4 magnets and the stuff just gets sucked in as fast as it is produced.
Where is the NH4 produced?
A tiny amount in the substrate but it's recycled by bacteria. The water
column is where most of the NH4 is produced. And it's never measured since
it's being used as soon as it's produced. Oversized filter systems etc on
fish only tanks can do this as well but they build up NO3 as the end
product. We tend to run out of NO3 also and never measure NH4.
> 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.
Well if the plants are growing well/pruned regularly, they are going to be
able to remove a great deal of NH4, more than the bacteria which will adjust
to the NH4 available to them.
I don't know, I do not know the uptake rates for the bacteria but these can
be assayed for density with small amounts of NH4 added(fish, salts, etc) on
agar media plates with plants, in tanks plate counts etc both with and
without plants present.
Hummm, that would be fun to do actually.
Bacterial-plant competition for NH4+ (also NO3 and denitrification).
>> 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.
Tropica did do one case study. But it's difficult to say. They found optimal
flow rate of 0.49 liters/day/m^2. This is about normal diffusion.
But there are many variables in folk's tanks.
I slope my gravel in all my tanks generally. One area is 1 inch and the rear
maybe 6-8 inches deep. Certainly diffusion with coils or diffusion alone
will have different rates along with grain sizes.
I've replaced poorly set up cables that use grain sizes that were too small.
The exchange works if the depth and pore size are correctly done, but folks
invariably find ways to find Murphy's law.
But you can do flow experiments without too much trouble if you use the
RFUG's. These flow rates can be varied, this would especially work well
using something like a peristalic(sp) dosing pump which can be precisely
Using relative growth weights of the dried plant materials you could gauge
the volume produced at each flow, root volume, generally plant health on a
relative scale etc.
>> 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.
Me too, I loved those RFUG for sometime. Still do for "fish only tanks" but
I could not ever have a fish only tank without plants:-) I'd go straight to
Plant tank Hell and be forced to pick off BBA for eternity.
>> 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.
Well, I solved this issue by either adding loads of laterite to start with
or simply switched to Flourite, which will never run out and is even _more_
>>> 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>.
Schmee level, Sea level. I've been the only one with cables with the Sfbaaps
group. Steve, Jeff, Erik and others had very nice tanks without any cables.
I'm talking very nice looking Amano like tanks. Nothing but sand + laterite.
Later folks added some peat.
4 clients that had Dupla cables in the past for a number of years switched
to the flourite. All have been happy, reporting better color, better plant
Heck, I saw it many times. But these folks did not tend the plants as much
as I. I switched my home tanks eventually and really saw marked improvement.
Now it might be that the cables + laterite might do a little better or a
reptile pad+Flourite. That would be a good long term test.
I'm betting no one would ever find any difference between a Flourite tank
w/rep pads vs the Flourite tank with cables. Same for the sand/laterite
But I think the point is that I have a nicer tank/plant growth without the
cable/sand type tanks using plain Flourite without cables/pads/RFUG's etc.
That is convenient/simple.
>> 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.
I've never had one of these except when I roasted a few Aponogeton bulbs
with a cable set up a couple of times. Remember those hot point source
cables instead of the nice even warmth of a reptile pad? I've yet to have an
anaerobic substrate except where I put a very slow growing or half dead
plant bulb, crypt etc and then did not give it enough light/nutrients etc
and it decomposed. You have to add some organic matter in large amounts in
order to produce the H2S. I've had this happen in RFUG's the least, a number
in heating cables and a few times with no flow. But in all cases it was me
putting a rooty plant deep in there and torturing it so that it died back
leaving a bunch of rotting material down there to form H2S.
A substrate can be 12" deep etc and not go anaerobic unless you add some
organic matter for the sulfur reducing bacteria to use.
I don't think there is anything inherent in the substrate flow systems that
prevent this. Only at very high rates of flow will this really have much
>>> 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?
Light is the main thing these weeds compete for. There's plenty of water,
generally plenty of nutrients within the substrate. CO2/carbon to some
degree as Hydrillia is darn good at beating any other plant/algae at this
But the worst weeds are not beating the competition by allelopathic
chemicals. This is a subtle and often extremely difficult test to perform in
water. Adding a substrate also will make it even more complicated.
Think about the worst weeds, Hyacinth, Pista, Salvinia, Hydrillia, Lemna.
4 of them beat the others by light and Hydrillia does to a certain extent
with floating mats + good Carbon concentrating mechanisms.
>>> 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"?
I smell Bait.
If you don't do water changes for years, although it can be done, you are
simply being lazy and the wife should give you a whack on the noggin:-)
But actually the DOC/tannins/etc builds up only to a certain point and then
levels off in most systems(I'll assume tanks as well). They do decompose and
it takes awhile.
The tannin levels here stay pretty close to the same which is interesting
since they are suppose not to decompose easily or for a long time. But if
that were true then the levels of tannin would continue to increase in some
of these system but we do not see this.
Bacteria is likely breaking it down after some time or after it gets to a
Years or months, I think the same applies.
But doing water changes reduces the unknowns of DOC/allelopathics/poor test
>>> 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!
Here you go Ebenezzer:)
Tropica's ref's at 0.49 liter per day per meter squared as the optimal from
what they found. Claus doesn't suggest folks to use them. He might have some
more references on it, I look/research at natural systems rather than doing
so many tank experiments lately. Although I will have some O2/CO2 effects on
periphyton (attached micro communities on your plant leaves, mainly algae)
coming up in about 3 weeks or so.
>> Where is George? He better come to Dallas for this year's AGA meeting!
> Well, that's up to Karla!
George, can she be bought? Every boss has her price(At least mine does).
There must be something she wants? Remember, those behaving well points take
a while to accumulate and MUST be done prior to the request, never
afterwards. If you are doing it to make up for past poor behavior, your dead
meat. Goodie points must be earned in _advance_ to be of any use.
I don't make the rule, I simply follow and obey them like you:-)
Get ahead now so there will be a "maybe" later.
Maybe we can put your name on the AGA workshop series?
Then it's for the good of the fellow hobbyist.