Re: Anaerobic Substrate? sulferous smells

> From: Albert Salas <AASALAS at aamc_org>
> Background:  I had used just a gravel substrate, but after I got the plant bug,
> I set up a (yeast/sugar) CO2 dispenser & began administering a few drops/day of
> Kent Freshwater Plant supplement 7 added dupla-type "pellets" around the base
> of selected plants; peat around others. [snip]
> vacuuming through top of gravel.  I use peat in the "whisper" filter.
> Problem:  It all stopped.  The echinodorus turned yellow; sags began dying off;
> hygros became stunted & stopped growing. (tho' pieces of hygros that float seem
> to stay healthy.)  Even the duckweed has disappeared, after first seeming to
> yellow out.  In the aquarium w/o oto's, everything got covered with diatoms (I
> believe that's what they are based on some exchange in this listserve).  Only
> the anubias & crypts seem to still be somewhat healthy.  When vacuuming the
> gravel, I get a strong, sulphury smell.

A certain amount of smell from an aquarium is normal. If you've ever had
blue-green cyanobacteria (slimy coating), acquaint yourself with the smell
of this; it's quite strong but distinctive.

From the description of your substrate, I don't suspect H2S formation in
a large concentration. The reactions of your plants are more typical of
a nutrient deficiency; Neil Frank gave the following information on
the subject in the 25 Jun 95 APD:

From: nfrank at parsifal_nando.net (Neil Frank)
Here is a table I adapted from
 Jacobsen, Niels. AQUARIUM PLANTS (1979). Blandford Press Ltd.

It extends the information recently provided on the digest by David Whittaker
 about mobile and immobile elements.

Other useful information can be obtained from
 Krombholz, Paul.  "Mineral Nutrition of Aquatic Plants, Part 1"

            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.
                                Inhibited flowering
(*)  The plants may also become reddish from the presence
     of the red pigment anthocyanin.

(**) Although Jacobsen does not differentiate between new and old leaves,
     David Whittacker reports from a hydoponics book that boron, calcium,
     copper, iron, manganese and sulfur are immobile elements and whose
     deficiencies affect new leaves.

Have you tried the addition of nitrate (KNO3 per PMDD recipe) or
a chelated iron supplement? Your duckweed should respond and improve
almost immediately. I suspect that your tanks originally had a
good supply of organic nutrients which had collected over time
but that with strong lighting and vigorous growth, these were
used up.

Since your substrate is quite old, I expect that you have quite an
accumulation of organic materials in there which are decaying and
could be contributing to a sulpherous or rotten egg smell which
indicates H2S. Aquatic plant roots are well adapted to deal with
this by providing a zone of oxygen around the root hairs. Also the
top layer of the substrate contains oxygen for several millimeters.
This oxygen will oxidize H2S and greatly reduce its toxicity.
Nitrate and iron also act as oxidants to remove H2S. Iron is
particularly _important_ as a soil component. This is one of the
VERY important reasons why an organic substrate needs to contain
a large proportion of mineral substances in relation to the organic
substances. Studies conducted by Barko & Smart indicate that _natural_
sediments with an organic content of about 5% were most optimal for

Most top soils (or those suitable for agriculture) do contain a
very large amount of iron compounds. Several people have had very
good results using different combinations of these loamy types of
soil. Jim Kelly used small quantities of loam top-soil mixed with
vermiculite. Paul Krombholz uses a layer of top-soil which he
mixes to form a mud and then screens to remove excess fibrous
material. Both soils have a covering of sand or fine gravel to
aid planting and somewhat dimish the problem of mud clouds when
removing plants. Paul puts his soil in trays so it is easy to
remove them and renew them to improve fertility periodically!

The Dupla laterite method and other laterites and iron rich clays
have also been quite successful and I suspect that the iron plays
a very important role.

While we can get very good growth using organic substrates for a period
of time. One of the problems we need to solve is how to maintain the
fertility of these substrates over time. Natural substrates get enriched
by fresh layers of detritus, dead algae and eroded mineral sediments
which continuously build up. In the natural environment the quantities
of sunlight can be much more intense and the plant has a much greater
depth of soil in which to send its roots. The plants grow far less
densely and growth is typically seasonally cyclical. We cannot easily
duplicate this environment. I don't think the results would be all
that aesthetically pleasing anyway.

I've mentioned some other strategies for enriching your substrate
previously so I won't repeat those again at this time. There have
been a few postings here and on the RAFP newsgroup concerning the
use of soil substrates. I know I've often mentioned the use of soils
and had good intentions to write up a FAQ covering this and other
substrate issues. I feel I need to mention just some of the
precautions that folks need to be aware of. I should also cover
precautions for collecting soils but time and space don't permit.
Bug me again and I'll cover that later. I just want to make sure
that people are aware of the important things to know about before

I recently covered another potential mistake of soil duffers on
the RAFP newsgroup. It had the indications of an oxygen deficiency
since it looked like too high a mix of organic to mineral in
his choice of soil. I think he used straight potting soil which
sometimes contains about 90% organic sphaghnum moss or other
partially composted organic materials.

I hope this helps cover some of the pitfalls of using soils and
I hope that some of the other people using various soil types
(and we can include laterite, peat and anyting else in the
category of soil) will add a few comments or criticisms /

Steve   spush at hcsd_hac.com    Vancouver BC Canada