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Re:Growth problem & anaerobic substrates
dhr. de Reus <j.de.reus at tip_nl> wrote:
>Subject: Growth problem with aquatic plants
>older leaves of the plants become curled and hard and
>sometimes drop off. Especially Lobelia Cardinalis shows these
>kind of symptoms but also Ludwigia Repens, Hygrophila Stricta
>and Althernanthera Reineckii. The H. Stricta develops small
>brown spots on the older leaves which eventually drop off.
In my experience, the loss of lower leaves is common wth H stricta,
Lobelia and A reineckii and this is aggravated by potassium
deficiency. With loss of lower leaves with Ludwigia (as well as
Bacopa and H poly), is a sign of potassium deficiency. H strica and
other rapid growing plants seem to show deficiency symptoms sooner
than others especially under higher lighting where other nutrients
are sufficient. That's because these fast growing plants utilize
an "optimistic" growth strategy. Who was it that mentioned the
two growth strategies about a year or so ago? Charlie Bay?
>I found in the archive of the aquatic plants mailing E-mail list
>a table by Neil Frank with nutrient deficiency symptoms and
> it looked as if there was a potassium deficiency.
Yes, I think you can find the same table in the TAG back issues
and the Krib. It has been expanded upon (mobile nutrient deficiency
symptoms show in old leaves) by David Whittaker.
The original table posted by Neil was in TAG 6:5 and came from
Jacobsen, Neils - Aquarium Plants (79) See also another article
in TAG 8:5 by Whittaker. The following table also includes some info
from Paul K.
COMMON SYMPTOMS OF NUTRIENT DEFICIENCY IN AQUATIC PLANTS
Leaves to first
Element show deficiency Symptom
Nitrogen Old Leaves turn yellowish (*)
Phosphorus Old Premature leaf fall-off
Similar to nitrogen deficiency
Calcium New Damage and die off of growing points
Yellowish leaf edges
Magnesium Old Yellow spots (*)
Potassium Old Yellow areas,
then withering of leaf edges and tips
Sulfur New Similar to nitrogen deficiency
Iron New Leaves turn yellow
Greenish nerves enclosing yellow leaf tissue
First seen in fast growing plants
Manganese (**) Dead yellowish tissue between leaf nerves
Copper (**) Dead leaf tips and withered edges
Zinc Old Yellowish areas between nerves,
Starting at leaf tip and edges
Boron New Dead shoot tips, new side shoots also die
Molybdenum Old Yellow spots between leaf nerves,
then brownish areas along edges.
(*) The plants may also become reddish from the presence
of the red pigment anthocyanin.
(**) Although Jacobsen does not differentiate between new and old
David Whittacker reports from a hydoponics book that boron,
copper, iron, manganese and sulfur are immobile elements and whose
deficiencies affect new leaves.
> So I added once a week a teaspoon of K2SO4 to my 500 l tank.
I think this may be too much. 1/8 tsp in 10 gals will give about
10ppm so for 80 gals you could add 1 tsp and then 1/8 tsp for each
10 gals of water you removed and replaced. Other folks just add a
tsp whenever it looks like there's a deficiency. This requires
you to be experienced enough to know the symptoms when you see them
so I prefer the dosing method. The actual concentration of K is
not critical over a wide range but I believe Dave Huebert or somebody
described the overdose symptoms a few months back. As has been said
recently, we sometimes give pat answers so you may need to scrutinize
the symptom descriptions and decide if any other nutrients might be
absent. The mobile nutrients are: zinc, molybdenum, magnesium,
nitrogen, phosphorus and potassium. The immobile ones are boron,
calcium, copper, iron, manganese, and sulfur.
>used Dupla24 fertilizer (10 drops every other day) and 10
>drops every other day of my own PMDD based on EDDHA
>(sequestrene manufactured by CIBA GEIGY). CO2 is
>added to the tank by DIY sugar and yeastmethod.
hmmm... my first reaction is to think you're mixing several
methods together and perhaps overdosing certain things. My
understanding is that the Dupla24 and the Dupla tabs are a
complete nutrient strategy but I would defer judgment to George
on that call! ;-) One of these days, I'm going to write a long
article (probably for Neil Frank) on a simplified low cost
strategy designed for a wide variety of plants.
>After adding the K2SO4 some plants really took off
>especially Hygrophila Difformis and Hottonia Inflata. But
>once again the older leaves became blotchy and ugly.
>Large holes appeared in the leaves of Barclaya Longifolia.
>Also beard algea and hair algea showed up. IMO it is clear
>that the plant are lacking one or more specific nutrients.
>Can somebody give me a hint of which nutrient(s)
>my plants are missing?
The appearance and proliferation of filamentous algaes (beard
and thread) may indicate a higher than optimal amount of chelated
iron in the water. My guess is that the Dupla drops are more than
necessary but I'll defer to the acknowledged experts on Dupla.
It's difficult to determine if there is enough magnesium from
the parameters you've mentioned. You mentioned using your own
PMDD mixture so perhaps you have some amount of magnesium (aka
Epsom salts) in that. The other mobile elements which we cannot
discount (zinc and molybdenum) are trace elements so the loamy
soil or other additives probably have that covered. If the other
plants are growing rapidly and appear healthy I don't know what
to suggest beyond that. Perhaps a excess of something... I think
Dave H mentioned that very high concentrations of K can inhibit
the utilization of other nutrients.
>Fe level (no level detectable with my Dupla testset)
I'm a little suspicious of iron test kits... I think we need
to determine if the amount of Dupla-24 you are using is appropriate.
That's not the cause of your problems with the lower leaves but
you may be interested for other reasons (like reducing algae
Dave Huebert <eworobe at cc_UManitoba.CA> wrote:
>Subject: Re: anaerobic substrates
>BAD THINGS that can happen;
>Gases such as sulfide, methane, nitrogen or combinations of
>these can be formed.
I'd like to add one or two (dozen) points to Dave's excellent remarks.
All substrates are anaerobic (or more correctly anoxic, without
free oxygen) below about a half inch of the surface. As you go
deeper down the oxidizing chemicals get used up by certain bacteria
types (aerobic, facultative and anaerobic). This change in chemical
(biochemical) balance is called the redox potential. It is positive
in oxygenated water (600 mV) and decreases below the surface of
the substrate according to depth. It reaches a minimum value (~150 mV)
at about 5-6 centimeters of depth in nature. With unnaturally high
of labile materials (such as from potting soils etc) I think you might
get the -150 mV redox potential at a shallower depth. Note that methane
formation does not occur until below -150 so contrary to what I'd said
in a previous article, sulferous substrate bubbles may be primarily
nitrogen. Certainly if they're not smelly.
The following table helps describe the relative reduction processes
which occur at these redox potentials:
the Sikora & Keeny paper "Further aspects of soil chemistry under
conditions" 1983 in Mires: swamp, bog, fen and moor. Elsevier,
The Netherlands. table 6.1:
Possible systems operating in flooded environments as related to
redox potential (Takai & Kamura 1966 etc...)
System Redox (mV)**2 Micro-organisms involved
O2 disappearance +500 - +350 aerobes
Nitrate disappearance +350 - +100 }
Mn2+ formation below +400 } facultative anaerobes
Fe2+ formation below +400 }
Sulfide formation 0 - -150
Hydrogen, methane form. below -150 obligate anaerobes
Paul K supplied some notes from an older article: MORTIMER, C.H.,
The exchange of dissolved substances between mud and water in lakes. J.
Ecol. 29: 280-329.30: 147-201.
Mortimer made a graph of redox potential versus substrate depth in mud
an eutrophic lake and also in mud from an oligotrophic lake. In the
2 cm. of the eutrophic mud the redox potential went from 600 mv to about
mv. It reached a negative 100 or so mv. at about 5 cm. and then
increased a little with increasing depth to about 0 again. The redox
potential in the oligotrophic mud dropped to about 150 mv. at 5 cm. and
then stayed the same thereafter. He gives ranges for verious reductions
plant nutrients that differe a little from those you cite above:
NO3-----> NO2 0.45 to 0.40 volt
NO2-----> NH4 0.40 to 0.35 volt
Fe+++ ------> Fe++ 0.3 to 0.2 volt
SO4 ------> S 0.1 to 0.06 volt.
Note that the sulfur reduction is to S, not S--.
The presence of labile (decomposible) organic materials below
about 2 inches of depth will probably lead to a redox potential
sufficiently low to produce sulfides. The long and the short of it
is that there isn't much point in putting organic components deeper
than 2 inches except for very small amounts of humus such as you
would get by removing all the organic fibers from a soil as Paul K does
to get his mineral soil. You could mix a small portion of this with
silt. Dupla laterite has about 0.1% humus I think. You need very
little to get the redox low enough to reduce iron and manganese
to their soluble states. A layer of soil 1/2 inch deep is quite
sufficient. The point of having anything deeper, I think, is to
increase the volume so that your can get enough root area for
certain plants to get enough iron. That may be a moot point if
you're going to add chelated iron such as by PMDD, Flourish, Tropica
Master Grow, Dupla-24 etc. Not withstanding, I believe that most
rooted plants grow much better with iron compounds in the substrate
such as laterite, iron rich clay, soils, micronized iron...
These iron compounds are important to the phosphate processes
which Dave aluded to since iron binds with phosphate in such a
way that plant roots can get at it.
When we talk about the bad things in an "anaerobic" substrate,
we should probably use more accurate terminolgy such as low redox
potential coupled with excess labile material. Anaerobic means
without air whereas anoxic means without oxygen. There are other
chemicals which exist in differing concentrations within the
substrate near the surface which also act as oxidizing agents
such as nitrate and at lower redox even sulfate.
>A large nutrient release can occur as the substrate becomes
>anaerobic. This may cause algal blooms. Again, to deal with
>this problem, submerge your substrate in a large pail and
> let it sit for some time. Another solution, of course, is
> to place 1" to 1 1/2" of coarse sand on top of
>the fertile substrate to act as a seal.
I've not been successful in getting coarse sand to act as a
barrier to ammonia and nitrates. I'd recommend people avoid
overly fertile materials or leach them in pails as Dave suggests.
By the way, you can expect a pail of mud-water to go low-redox
and produce mercaptan (sulfer) gases since it has no oxygen
sources such as plants and the soil is probably too deep to
permit oxygenated water to penetrate. I don't know if that's
bad. It should liberate a lot of the nitrogen and phosphorus
compounds so that they can be leached out. I'd like to hear more
about it if somebody tries it.
Paul K has mentioned he doesn't worry about the nutrient release
with most of his soil substrates because he usually grows them
without fish and using daphnia which happily eat the green water
I found ammonia production occured within the first few months
of submergence so this ought to be monitored weekly. Usually
makes stuff grow like mad and not all types of plants were able
to grow well using the earthworm casting substrate. If they had
strong, established root systems, I think most plants would have
grown ok. Crypts had no problems under these conditions and showed
no tendency to Crypt melt. I think they are at a disadvantage
under "typical" conditions and this is why they are thought to be
slow growing. YMMV.
Steve Pushak in Vancouver BC
Please note the new email address: teban at powersonic_bc.ca
spushak at hotmail_com should also work even if I change ISPs.