[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[APD] RE: substrate eH investigation [technical, long]
I'd be real curious to know if the eH in a rich substrate [see below] got
down into the S reducing potential? And if it did, were there negative
side-effects? You're right, I don't think there's much to gain from a
precise eH profile. I guess the difficulty is in determining if/when there
are negative side-effects. We want to consider the effects on fish,
invertebrates, bacteria & algae. If the study were to examine intermediate
parameters such as eH, then it has to consider toxins (see below Barko &
Smart remarks) as well as nutrients. I'm inclined to think that using the
most stable OM, peat (or humus/mulm) & keeping N & P only as simple salts
occluded within clay would hopefully prevent the undesirable biochemical
reactions. N is needed for bacteria to breakdown peat lignins further.
I've grown plants in soil substrates of various depths & composition. Using
an artificial soil, earthworm castings, I had very rapid growth for a number
of months. H stricta developed a deficiency problem with yellow veins that
was cured by N additions to the water, so N provision in a soil substrate
will only last a few months unless special steps are taken to occlude it &
prevent bacteria from having access to the other nutrients, carbon among
others, necessary to produce N2 gas (denitrification). Using clay balls I
can provide N & P to plant roots & regularly amend it. Its not always easy
to know when the N is no longer enough but we could estimate by dry/wet
plant mass ratios & average N content. It seems wise to provide a little N
in the water because some plants with high N demand may not be able to get
it fast enough from a clay ball; maybe root growth needs to penetrate the
One of the problems with using a "messy" amendment like peat, soil or clay
in a general substrate is that when you remove plants, you can liberate a
lot of nutrients, perhaps even DOC and this seems to trigger BGA. At the
least, it makes a mess.
If I put the same plants into ceramic pots, I can use much richer amendments
& simply lift the pots out to harvest them. Practically no mess at all when
you put the pot back into the tank, simply adding a little gravel to cover
the hole made digging out a hunk of Crypts for example.
Pots also help to prevent or forestall the tendency of some Crypts to spread
throughout the tank. The problem with a pot containing C blassii is that
eventually it becomes quite root bound & the plants do not attain their
magnificent size. On my website are pictures of C blassii which I grew
several years ago; with leaves which were 2.75" wide and 11" long. The stems
were about 17" on this plant so the overall length was about 28" and from a
healthy specimen it attained this size in only a few (4-6?) months. I don't
think you can grow something like that hydroponically. I was not able to
duplicate this feat using an 8" diameter clay pot about 4" deep with soil &
clay fertilizer balls. Perhaps if I used earthworm castings with a clay cap
it would have worked better. I got the idea of using pots from Karen Randall
but I don't think I've fine tuned that approach yet.
A few years ago, I believe I gave Karen some C blassii which I think she
might have shared with Neil Frank. I don't know if either have been
successful in getting the large specimens. I seem to recall Neil saying
something about not having red under leaf with other C blassii samples he
had. Perhaps there are differences in the C cordata cultivars. Karen, Neil?
In the deep cube tank I had a very deep substrate in those days. I know I
had S reduction in there. It didn't come out unless I disturbed the
substrate significantly such as by uprooting a giant Amazon Sword which I
had there for a while. I think low redox is less of a problem than we might
think. I think it bothers plants not at all because their roots prevent low
redox as they grow & penetrate. A freshly planted specimen might be
susceptible I suppose but the plants seem to recover quickly growing new
roots until the root-shoot ratio is back to what it should be. Crown plants
are the most easily killed but the crown should always be planted above the
surface, where redox stays quite high.
I think next time I try C blassii, I will use a 1 gallon or larger pot and a
mixture of peat & earthworm castings, fine steel wool or micronized iron and
a clay cap covered by gravel. Throw in some big clay-fertilizer balls; what
the heck! It might be wise to stay away from sulphate based nutrients.
Paul K uses trays, not too deep. Have you ever tried deep substrates Paul?
Thomas, as you mention about a stable substrate, I think peat is a good
candidate for providing organic matter & its pretty stable with virtually no
N or P available. Substrates with N and possibly P & of course Fe certainly
seem to grow big plants quickly. The deep substrate may even have
contributed to a much higher CO2 concentration than I typically provide
using injection. The thing about an N enriched substrate is that its going
to deplete over time so the dosing regime needs to be modified to a more
hydroponic one. My two largest tanks are nearing 5 years & I've not enriched
them or changed the soil in the pots or in the other tanks with continuous
Initially, its probably easier to maintain an N enriched soil substrate
because you don't need to worry so much about regular N dosing
hydroponically. You get early great growth but the gotcha is that you may
need to modify the regime to more frequent N dosing hydroponically. Crypts
can get along fine with N limitation in the water but if you keep fish in
the tanks and feed faster than the plants can grow, skimp on water changes a
little and you end up with BGA. :%]
Regarding organic content, you've mentioned some studies that indicate 20%
OM is too high. The Barko & Smart study indicated that natural sediments
above 5% OM had declining productivity. I can't recall if the discussion
suggested that low eH might have played a role; I've misplaced those papers
somewhere in the move to this house. I recall they thought there might be
some organic toxins such as aldehydes, alcohols that came into play in high
When we talk about soil substrates, especially rich substrates, or deep
substrates, its probably more of interest to specialists such as Crypt
growers or for Lace plants. Some recent increases in my N hydroponic levels
for the benefit of the Lace plant, seem to have made the Crypts grow very
fast too. I've moved away from fast growing plants primarily into Crypts,
ferns (Bolbitus, Java) & Anubias but its trickier maintaining high fish
bio-loads with those slow plants.
Soil substrates aren't automatically bad for newbies; its just a different
regime & I'm beginning to understand that it needs to change over time.
Since y'all seem to agree that others on the APD might be interested in this
discussion I've included the most recent comments & edited in a couple of
> -----Original Message-----
> From: Thomas Barr [mailto:tcbiii at earthlink_net]
> Sent: December 12, 2003 7:12 PM
> To: Steve Pushak; Karen Randall
> Cc: huebert at mts_net; Paul Krombholz; Neil Frank; S. Hieber; George Booth
> Subject: RE: substrate eH investigation
> Well, the notion of something stable, not influenced by us digging and
> groping around down there or roots coming in pumping O2 to change things)
> is a good idea.
> I think the grain's themselves should possess the needed aerobic/anaerobic
> This way even at the surface of the gravel, there are available nutrients
> for foreground plants should they need them.
> I think trying to remove everything from the substrate and testing/dosing
> just with the water column alone...................
> Then you start adding things to a substrate and note the differences for
> each change.
> But getting the water column correct is a key point here.
> I've done this and the main nutrient that I think needs to be in the
> substrate is Fe.
> Even if you maintain the best water column conditions, this
> nutrient still
> needs to be in the substrate.
> It's not for it's PO4 binding either. I've done enough PO4 dosing work to
> know that's not it. I also had lots of PO4 and no iron in the substrate
> also, so the changes could not have been attributed to PO4 in the
> The Eh's of interest will be for Fe, NO3 denitrifyers and sulfate
> I think losses of NO3 gas to N2 gas are small. The levels of NO3 do not
> fall if you cut off the CO2 and other nutrients. There's also
> less O2 so it
> would be more ideal conditions to produce N2 gas by the microbes.
> Sulfate reduction you simply do not want.
> So this leaves iron, and NH4 but there's not much produced and if it is,
> bacteria and plants roots likely recycle it rapidly like they do in the
> water column.
> So there's iron and what else? Organic matter.
> Just those two + a good gain characteristic and you have a pretty good
> substrate that will produce the Eh's evenly and consistently
> where you want
> Now if you want to talk C. cordata blassii, I've flowered it submersed,
> emersed, had them get an inch or two from the top of a 55 gal tank.
> So while you may want to tout soil/rich OM substrates, they
> certainly don't
> seem to be a requirement.
> I have trouble seeing a decent correlation with anything Eh related except
> If I was going to look into something here dealing with Eh, it would be
> with iron in the substrate.
> Try these different methods out, try using substrate that is fairly inert,
> try RFUG's, Cables, Flourite etc etc etc. Observe the plant's responses.
> I think many folks would see the same thing.
> But you have to control both the water column and the substrate because
> these plants will access both, if you plan on working on this or else do
> emergent study.
> Tom Barr
> > [Original Message]
> > From: Steve Pushak <teban at powersonic_bc.ca>
> > To: Karen Randall <krandall at rdrcpa_biz>; <tcbiii at earthlink_net>
> > Cc: <huebert at mts_net>; Paul Krombholz <krombhol at teclink_net>; Neil Frank
> <nfrank at mindspring_com>; S. Hieber <shieber at yahoo_com>; George Booth
> <gbooth at frii_com>
> > Date: 12/12/2003 4:39:33 PM
> > Subject: RE: substrate eH investigation
> > I'm curious if anyone else has any ideas about how a redox investigation
> > might be useful (or not).
> Thomas Barr wrote:
> > Steve P wrote:
> > "What I would be most interested in learning in the planted
> > aquarium would be
> > the eH at the bottom of a soil+peat substrate approximately 3"
> > deep. I'm not
> > at all concerned about the profile of eH with depth; we know it will
> > continuously in between the level at (or near) the bottom and the level
> > well-oxygenated water at the surface."
> > I an predict it, I'd say about 200mv depending on grain size and
> > organic matter content.
> Can you quantify with real data?
No, but generally this range and the amount of electron acceptors and
donors would be close or a tad higher depending on the organic matter
content loaded into this system. If it was lower, say if you add more
organic matter, H2S is produced.
> > "Even a single data sample taken in an established tank would be quite
> > useful."
> > For what?
> There has been considerable speculation about redox, effects & causes but
> substantive investigative work. If there is a range of acceptable mixtures
> of peat, soil, compost, sand, clay what are the limits of that range? When
> do bad things happen as a result of low eH, if ever? We can speculate that
> bad things will happen when eH goes below zero but do they really? No
> No evidence.
Well, it takes something to lower the Eh, like no O2, organic matter( a
source of electron donors), no flux in/out, no roots in these regions(These
transport O2, which raises the Eh)
There is evidence from aquatic systems and wetland soils, volumous amounts.
Search "Everglades" and "WCA-2".
They typically will list in their data the amount of Organic matter(OM) in
>From that you can make some estimations.
Even if you did a case study with a planted tank, the application would
needed to be taken with a grain of salt.
Such precise Redox measurements given the nature of plant roots seems
rather fruitless to me anyway. There's a redox maximum for optimal plant
growth but this is a general range and I think it will apply to most
There are also constructed wetlands, lab sized 1 meter cubed wetlands in
the soils lab here etc.
> > "Ideally it would be nice to set up a fresh aquarium and take
> > weekly for about 2 months & then monthly for about 6 months. In order to
> > test the assertion that eH increases with age in a planted substrate
> > has become root bound,"
> > Well that's not what's going to lower Eh, organic material
> > addition will almost always lower Eh. Healthy active roots will raise
> I would expect that eH will decline for several weeks & stabilize at some
> point & then rise again as the substrate becomes filled with roots. This
> one of the assertions that should be tested experimentally.
Sure, I agree with that, you can see this same thing when looking at redox
values for flooded upland soils with a wide variety of inputs etc.
I must have a dozen or so graphs depicting this, showing what happens over
time as an upland soil is flooded/dried out and reflooded etc.
Paul suggest placing the soil slurry into a bucket for a couple of weeks
first before adding the soil to a tank. This, in effect, speeds up the
But then again, what do you hope to gain by doing this in a tank?
The plants alter things here and that's WHAT we are trying to grow, not
develop some Eh layered set up.
That's why we see excellent growth with RFUG, Cables and with
Omosis(Flourite or soil)
These redox values are different in each type of system.
But around the roots, it's likely the same.
> > I don't think you will gain much by looking at the depth layers
> > or some semi standard depth/peat mix etc.There's too much
> > variability and other competing interactions going on.
> I think we should expect to gain more insight into the use of soils & peat
> in substrates. I think we should investigate more than what is simply
But I do not see better growth as a result of differing Eh's in substrates
so again I question the value of this. I know what is required to do this
test and yes, i have access but I am not remotely convinced it will help to
grow plants any better.
I stick with the big picture. Will it grow plants better?
Yes or no.
> I would like someone with access to redox equipment & with knowledge of
> substrate processes to perform some investigation so that we can better
> understand the role of eH in a substrate & to de-mystify the use of soils
> and or peat in substrates, quantitatively. Specifically what range of
> mixtures are acceptable. What are the negative results & are they severe?
I have access for sure.
I think we may be able to find the relative % of organic matter in the
literature, but relating them to macrophyte growth might not be easy.
Wait, I do know this information actually, I recall about OM content above
20% is detrimental to aquatic macrophytes in wetland soil.
> > I agree, but the plants mediate their environment with O2
> > transport to their roots anyhow.
> > The nutrients are not harmful but.......... H2S is harmful to
> > plant roots and not a good thing.
> > You need a balance of organic matter, but too much.
> How much? How would you go about answering this question experimentally?
Easy, % of OM per unit of soil. You roast the Organic carbon at high temps,
weigh the mass balance.
The rest of the carbon left is carbonates and this also can be measured by
roasting it at even higher temps.
Some literature has suggested no than 20% OM is good for aquatic macrophyte
growth, above this amount, algae dominate.
This is for Florida wetlands and lakes.
Lotic systems(Rivers/streams) may be able to have more/less.
> reject growth experiments as having too many confounding problems.
Well, hobbyist are not scientist, many plain do not want to be. They want
an easy simple method. Repeating it is a key element.
Growth analysis is good, but it requires a lot of plant material and space.
These are things I ain't got and ain't going to give up.
I got 15N to play with and I can get some good data from that.
But most folks have a tough time replicating and preventing NO3, K, PO4 etc
from running out.
Few are going to grow enough plant material to have 500grams or so of dry
Yes, it can be done. But, few will do this for this reason for aquarium
Yes, we, or someone can come along and figure out that 5.8% OM in the form
of peat is optimal etc, but I think they will be very hard pressed to show
this is significant even after going to all this trouble, hobbyist have a
great deal of variation in their tanks.
There's a lot of range of OM % added and type and if the substrate has
iron, what types of NO3 levels, fish etc, all these things influence Redox
Eh values as they are electron donors/acceptors that certainly influence
the tank. Flow through to substrate, grain size differences, amount of
plants/density of the biomass of roots, current in the tank, lots of
But plants change things to what suits them so it gets back to that once
again.........if there's enough Fe, P, K, N etc, they do pretty well.
> plants will do much better if they have a deeper substrate. Why? Is it
> simply because there is a greater pool of nutrients available in a larger
More room to spread out. The OM is spread out also within the substrate, so
you can reduce the effects of pulling up some of the NH4 etc and the
substrate can handle more without as much build up in the water column. You
have the same nutrient/cm^3 but the total amount is high.
Root bound effects are also reduced.
Is it because a certain eH is necessary in order to maximize iron
I do not think so although it may help in subtle cases.
Mainly is the iron there(for the plants) and it keeps the Eh from dropping
too far(For the substrate) by buffering the Eh..
Can we maintain high iron availability by increasing the
> organic content to say 5% by weight using peat? Are you familiar with the
> work by Barko & Smart in this area?
Yes. They have done a number of studies.
I use peat also, so I like to add it to help jump start a tank with low OM
in the substrate.
It makes things a little easy till the plant's roots get going and are good
and healthy. It provides a source of carbon for the soil bacteria and I
also add mulm also to help seed and to provide a little OM as well that's
well broken down.
> > Flourite is nice because each grain is a porous micro-site that
> > has an aerobic outer layer and an anaerobic internal layer on
> > EACH grain. Then all that layering with sand, clays, peat, dirt
> > etc really is not needed, the degree of organic matter can be
> > less to get the same ranges of Eh's. You can also pull up roots
> > and replant without any issues to speak of.
> So your primary objection to investigating organic effects upon substrate
> processes is that its unnecessary given that everyone should use Fluorite?
No, I'm saying it's a good product that produces better plant growth
I believe that is the goal here correct?
Grow better plants?
I can talk about why I think it's good and provides a noticeable improvement
in many species.
> What about those of us who choose not to for any number of reasons?
Then you need to answer that question yourself. That's the way it works, if
you want to know, you need to do it.
I too am curious of how this may apply to aquariums, both FW and SW. So
there are good questions and it may help some.
But overall it might be something a company might add a certain ratio of
peat to their products etc or have fert balls etc with peat(or something
If you'd like, I know of an excellent on line course on wetland soils. You
can look over the materials if you wish as I might mail them to you
later(it's around 400-600pages).:)
Thomas Barr wrote:
> Steve P wrote:
> "What I would be most interested in learning in the planted
> aquarium would be
> the eH at the bottom of a soil+peat substrate approximately 3"
> deep. I'm not
> at all concerned about the profile of eH with depth; we know it will vary
> continuously in between the level at (or near) the bottom and the level of
> well-oxygenated water at the surface."
> I an predict it, I'd say about 200mv depending on grain size and
> organic matter content.
Can you quantify with real data?
> "Even a single data sample taken in an established tank would be quite
> For what?
There has been considerable speculation about redox, effects & causes but no
substantive investigative work. If there is a range of acceptable mixtures
of peat, soil, compost, sand, clay what are the limits of that range? When
do bad things happen as a result of low eH, if ever? We can speculate that
bad things will happen when eH goes below zero but do they really? No proof.
> "Ideally it would be nice to set up a fresh aquarium and take measurements
> weekly for about 2 months & then monthly for about 6 months. In order to
> test the assertion that eH increases with age in a planted substrate that
> has become root bound,"
> Well that's not what's going to lower Eh, organic material
> addition will almost always lower Eh. Healthy active roots will raise Eh.
I would expect that eH will decline for several weeks & stabilize at some
point & then rise again as the substrate becomes filled with roots. This is
one of the assertions that should be tested experimentally.
> I don't think you will gain much by looking at the depth layers
> or some semi standard depth/peat mix etc.There's too much
> variability and other competing interactions going on.
I think we should expect to gain more insight into the use of soils & peat
in substrates. I think we should investigate more than what is simply
> " you might have to wait a couple of years for the
> progression of a Crypt colony to become that established. If you
> used Bacopa
> instead, it would not take nearly so long. Paul once told me that
> Bacopa is
> able to convey a lot of oxygen into the substrate and it grows quite
> Yes, that's true. There are many species you can try but I really
> am not certain what the question is that you hope to answer by
> going to all this trouble.
I would like someone with access to redox equipment & with knowledge of
substrate processes to perform some investigation so that we can better
understand the role of eH in a substrate & to de-mystify the use of soils
and or peat in substrates, quantitatively. Specifically what range of
mixtures are acceptable. What are the negative results & are they severe?
> "The largest specimens that I ever grew came from my large cube
> tank with a
> 10" deep substrate. I was using a soil & sand mixture with clay fertilizer
> balls. I know that the eH was low enough to produce sulphurous smells"
> So that would be about 0 to -100mv range.
> Fe reduction at about 100-200, Mn about 150-200mv to 250-300mv or
> so and NO3 at 300mv range.
> that didn't bother the plants at all; their roots grew at the appropriate
> Well, of course, but the __root zone__ is NOT that reduced. The
> root will not live long otherwise if it cannot get O2 down there.
> " I did not find roots at the bottom of the aquarium but perhaps I
> would have if the tank had stayed active for more years. I had to move to
> this present location about 5 years ago & I used pottery containers
> exclusively in that tank. The C blassii has never achieved its previous
> glory and has continued to shrink as the container has become
> more crowded,
> even with thinning."
> C cordata var blassii is a weed. But if left alone it will do
> wonderful in rock hard or soft waters. The best plants I had were
> raised in 6 inches of Flourite, tons of CO2, lower light 1.6 gpw,
> triton/cool white mix, rock hard tap water, weekly dosings of NPK
> traces, weekly 50% water changes and a moderately to high fish load.
C blassii is a beautiful plant but it will not attain its magnificent size &
coloration in a container or a shallow substrate. You could also correctly
observe that all aquatic plants are in one sense or another weeds. Why did
the C blassii thrive in my deep substrate? See
<http://home.infinet.net/teban/> for a picture of the plant in question &
> "I think the biggest problem with using a "rich" mixture is
> necessarily the
> low redox (eH) but the problem of nutrient leaching into the water."
> Well low Eh will produce nutrients like Fe2+, NH4+, PO4 and if
> those leach out, it can cause issues.
> This is one reason I have always talked about CO2 being higher
> than you think you need.
> Plants will gobble these up fast if they enough CO2.
> "The idea
> of a clay "cap" to prevent nutrient diffusion is a novel idea; I'm not
> guaranteeing it would work mind you."
> Well, if you plan on not replanting/uprooting ever.
> "My point is that low eH is not really that harmful to plants.
> Steve P"
> I agree, but the plants mediate their environment with O2
> transport to their roots anyhow.
> The nutrients are not harmful but.......... H2S is harmful to
> plant roots and not a good thing.
> You need a balance of organic matter, but too much.
How much? How would you go about answering this question experimentally? I
reject growth experiments as having too many confounding problems. Aquatic
plants will do much better if they have a deeper substrate. Why? Is it
simply because there is a greater pool of nutrients available in a larger
substrate? Is it because a certain eH is necessary in order to maximize iron
availability? Can we maintain high iron availability by increasing the
organic content to say 5% by weight using peat? Are you familiar with the
work by Barko & Smart in this area?
> The mulm method works well and a little peat does also.
> It's not a precise thing, I doubt it ever will be, but a
> generally under shooting seems better for this than adding too much.
> Light will play a big role as will adding CO2 gas/Excel etc.
> As you add more light and CO2, the less dependent the tank
> becomes on the substrate and the more dependt it becomes on the
> water column to meet the nutritional needs of the plants.
> This why a non CO2 soil tank with less light works great for long
> periods without much maintenance etc fish feeding(fish waste=
> small amounts of plant food), water changes etc.
> But you can get great health and slow growth by adding CO2 to a
> low light tank.
> I think this yields the best combination.
I agree to this point however its tangential to our discussion.
> Flourite is nice because each grain is a porous micro-site that
> has an aerobic outer layer and an anaerobic internal layer on
> EACH grain. Then all that layering with sand, clays, peat, dirt
> etc really is not needed, the degree of organic matter can be
> less to get the same ranges of Eh's. You can also pull up roots
> and replant without any issues to speak of.
So your primary objection to investigating organic effects upon substrate
processes is that its unnecessary given that everyone should use Fluorite?
What about those of us who choose not to for any number of reasons? I'm
using a little sarcasm here to make a point but I really don't want to annoy
you, Thomas because you are the only person that I know currently with
access or interest in this type of investigation.
> Tom Barr
Aquatic-Plants mailing list
Aquatic-Plants at actwin_com