In this experiment I used the following greenhouse (i.e. emersed-grown) plants:

1. Ammannia pedicellata 'Gold' (formerly known as Nesaea …)
2. Hygrophila corymbosa
3. Pogostemon deccanensis
4. Rotala wallichii

Lights

Filtration

Temperature

Substrate

While in the first set (aquaria #1 to #4) a substrate for aquatic plants covered with a layer of pure silica sand was used, in the second set (aquaria #5 to #8) no substrate was used.

1st set → nutrient-rich substrate

2nd set → no substrate

• The organic substrate should contain enough N, P and micro-nutrients so these were not supplied to the water column; some of the N and P will leach into the water column.
  • I used a local gardening substrate for aquatic plants capped with a layer of silica sand.
  • In aquariums with no substrate, I used M16 stainless steel hex nuts inserted into small size (2") hydroponic net pots to anchor (secure) the plants.

Week #1 (day #9)

• All plants arrived in excellent condition

Week #4 (day #29)

#1

Substrate

HCO₃⁻

CO₂

pH 6.4

#2

Substrate

HCO₃⁻

CO₂

pH 7.1

#3

Substrate

HCO₃⁻

CO₂

pH 4.9

#4

Substrate

HCO₃⁻

CO₂

pH 5.2

#5

Substrate

HCO₃⁻

CO₂

pH 6.0

#6

Substrate

HCO₃⁻

CO₂

pH 7.0

#7

Substrate

HCO₃⁻

CO₂

pH 3.0

#8

Substrate

HCO₃⁻

CO₂

pH 4.0

• Algae & Cyanobacteria
  • From around the sixth week, green water/algae (in aquarium #5) and cyanobacteria (in aquarium #6) became a serious problem.
• Ammannia pedicellata 'Gold'
  • key events:
    • week #2-3: I was adding nitrogen (N) and phosphorus (P) to aquariums #3 and #4 to check if the impaired (deformed) growth of A. pedicellata 'Gold' [in aquariums #7 and #8] could be due to excess macro- (= N/P) or micro-elements
      • Following the addition of nitrogen (N) and phosphorus (P) to the water column in aquaria #3 and #4, the condition of A. pedicellata 'Gold' deteriorated:
        • spots appeared on some leaves
        • some new leaves slightly deformed
        • some of the stems have rotted away
      • ... still, I'm not sure if it's really related to the addition of nitrogen (N) and phosphorus (P)
    • week #3: I removed most of the bad (= brown/old) leaves in all the aquariums
    • week #4: Following the addition of nitrogen (N) and phosphorus (P) to the water column in aquaria #3 and #4, the condition of A. pedicellata 'Gold' deteriorated:
      • spots appeared on some leaves
      • some new leaves slightly deformed
      • some of the stems have rotted away
    • week #4: Plants in aquarium #6 had died (decayed), so I removed their remains
    • week #5: The plants [in aquariums #1, #3 and #5] were in very poor condition, so I removed them
• Hygrophila corymbosa
  • key events:
    • week #2: There is one interesting phenomenon in aquariums #1 and #3 → the roots grow out of the pot (as if they didn't find what they needed in the sediment and turned back into the water column)
    • week #3: I removed one flowerpot (= half volume) from aquariums #5 and #7, because it was getting too big and began to over shade the other plants
    • week #4: I removed the plants from aquaria #1, #3, #5 and #7, as most of them had already grown to the surface
• Pogostemon deccanensis
  • key events:
    • week #5: The plants [in aquariums #6, #7 and #8] were in very poor condition, so I removed them
• Rotala sp. 'Vietnam' (Rotala wallichii)
  • key events:
    • week #4: I removed the plants from aquarium #7, as they had already grown to the surface

Week #7 (day #50)

#1

Substrate

HCO₃⁻

CO₂

pH 6.3

#2

Substrate

HCO₃⁻

CO₂

pH 7.2

#3

Substrate

HCO₃⁻

CO₂

pH 5.1

#4

Substrate

HCO₃⁻

CO₂

pH 6.1

#5

Substrate

HCO₃⁻

CO₂

pH 6.2

#6

Substrate

HCO₃⁻

CO₂

pH 7.0

#7

Substrate

HCO₃⁻

CO₂

pH 3.1

#8

Substrate

HCO₃⁻

CO₂

pH 3.8

Diary

• Tank #1:

  • week #2:
    • A.pedicellata: deformed growth tips, older leaves turn brown to black, diatoms attach to them
    • P.deccanensis: older leaves turn brown (die off), growth tips do not seem to sprout new leaves, but instead shoots sprout from the upper part of the stems
    • R.wallichii: deformed growth tips and upper leaves
    • H.corymbosa: rapid growth, beautiful rich colors (orange-red at the top), straight leaves; roots grow out of the soil (!)
  • week #3:
    • A.pedicellata: significant deformities, but some leaves appear to be fine
    • P.deccanensis: growing, but quite slowly
    • R.wallichii: looks terrible
    • H.corymbosa: relatively fast growth, rich colors, straight leaves
  • week #4:
    • A.pedicellata: looks terrible, more rotting stems; only a few apices remain (all significantly deformed)
    • P.deccanensis: good growth and good condition
    • R.wallichii: looks terrible
    • H.corymbosa: has grown to the surface (harvest), excellent condition; roots growing out of the soil
  • week #5:
    • A.pedicellata: completely rotted
    • P.deccanensis: good growth/condition; lush root system
    • R.wallichii: began to recover => good growth and condition (!)
    • H.corymbosa: harvested
  • week #6:
    • A.pedicellata: ---
    • P.deccanensis: good growth/condition
    • R.wallichii: growth and condition look okay
    • H.corymbosa: ---
  • week #7:
    • A.pedicellata: ---
    • P.deccanensis: no change (i.e. good growth and condition)
    • R.wallichii: no change (i.e. good growth and condition)
    • H.corymbosa: ---

• Tank #2:

  • week #2:
    • A.pedicellata: older leaves are turning brown/black; upper leaves look quite good, but are slightly curled; diatoms are attaching to them
    • P.deccanensis: stagnant, older leaves are turning brown (dying), new ones are not growing
    • R.wallichii: looks quite good, straight leaves
    • H.corymbosa: slower growth, looks quite good
  • week #3:
    • A.pedicellata: relatively okay (but some leaves are a little damaged), but slow growth
    • P.deccanensis: only a few new shoots/leaves (very slow growth)
    • R.wallichii: good color, but condition questionable (seems fine, but most leaves appear broken/wavy)
    • H.corymbosa: good condition, slow growth
  • week #4:
    • A.pedicellata: passable growth, but not optimal; slight deformities
    • P.deccanensis: very slow growth
    • R.wallichii: rather stagnant, deformities of growth tips
    • H.corymbosa: slower growth, but excellent condition
  • week #5:
    • A.pedicellata: lower leaves completely rotten, a few stems also rotten; the last 4 stems remain, which [seem to] be growing slowly but quite well; a few roots are visible in the soil (but nothing extensive)
    • P.deccanensis: very slow growth (but there is some progress); smaller root system
    • R.wallichii: kaput
    • H.corymbosa: slow growth, good/excellent condition
  • week #6:
    • A.pedicellata: slow growth, condition quite good
    • P.deccanensis: slow growth
    • R.wallichii: ---
    • H.corymbosa: slow growth, good condition
  • week #7:
    • A.pedicellata: no change
    • P.deccanensis: no change
    • R.wallichii: ---
    • H.corymbosa: no change

• Tank #3:

  • week #2:
    • A.pedicellata: best condition, many new leaves (nicely colored and straight); older leaves turning brown
    • P.deccanensis: older leaves turning brown (dying), new leaves at the top
    • R.wallichii: growth tips deformed, some of them sprouting side shoots at the top, which seem to be fine
    • H.corymbosa: rapid growth, nice rich colors (orange-red at the top), straight leaves; roots growing out of the soil (!)
    • midweek, nitrogen and phosphorus added on a trial basis (!)
  • week #3:
    • A.pedicellata: relatively best condition, but a few stems from the bottom have rotted (but the tops remain undamaged)
    • P.deccanensis: growing
    • R.wallichii: looks terrible
    • H.corymbosa: fast growth, slightly wavy leaves and "crumpled" new leaves (which may be normal)
    • I continue to add nitrogen and phosphorus (!)
  • week #4:
    • I am no longer adding nitrogen and phosphorus
    • A.pedicellata: deterioration => spots on new leaves, deformation, more rotten stems; upper part quite good
    • P.deccanensis: good growth and good condition
    • R.wallichii: growing a little, but poor condition (deformation)
    • H.corymbosa: grew to the surface (harvest); slight deformation; roots growing out of the soil
  • week #5:
    • A.pedicellata: kaput
    • P.deccanensis: good growth/condition; good root system
    • R.wallichii: recovered significantly => rapid growth, good condition
    • H.corymbosa: harvested
  • week #6:
    • A.pedicellata: ---
    • P.deccanensis: good growth/condition
    • R.wallichii: good growth/condition
    • H.corymbosa: ---
  • week #7:
    • A.pedicellata: ---
    • P.deccanensis: no change
    • R.wallichii: no change
    • H.corymbosa: ---

• Tank #4:

  • week #2:
    • A.pedicellata: a number of new leaves (quite nicely colored and straight, but smaller than in aquarium #3); older leaves are turning brown
    • P.deccanensis: stagnating, older leaves are turning brown (dying), new ones are not growing
    • R.wallichii: rather stagnant
    • H.corymbosa: slowest growth, smaller leaves, signs of chlorosis in older leaves, leaves appear slightly wavy/deformed
    • nitrogen and phosphorus added midweek on a trial basis (!)
  • week #3:
    • A.pedicellata: slow growth
    • P.deccanensis: stagnant
    • R.wallichii: rather stagnant
    • H.corymbosa: twisted leaves, chlorosis
    • I continue to add nitrogen and phosphorus (!)
  • week #4:
    • No longer adding nitrogen and phosphorus
    • A.pedicellata: relatively good condition, but slower growth
    • P.deccanensis: rather stagnant
    • R.wallichii: stagnant
    • H.corymbosa: good condition (straight leaves), but slow growth
  • week #5:
    • A.pedicellata: lower leaves rotten, upper leaves appear to be in good condition, but slower growth; a few stems rotten
    • P.deccanensis: rather stagnant (it seems that there is some positive growth, but very slow)
    • R.wallichii: rather stagnant and overgrown with tufts of algae/cyanobacteria; condition is not entirely bad (just practically not growing) => perhaps the [apparently] good condition may be the result of short-term addition of nitrogen and phosphorus in previous weeks (when I stopped adding it, growth stopped)
    • H.corymbosa: slow growth, fairly good condition
  • week #6:
    • A.pedicellata: slower growth, good condition
    • P.deccanensis: very slow growth
    • R.wallichii: stagnation
    • H.corymbosa: slow growth, good condition
  • week #7:
    • A.pedicellata: no change, but cyanobacteria began to grow on it
    • P.deccanensis: no change
    • R.wallichii: no change, but completely covered with algae/cyanobacteria
    • H.corymbosa: no change

• Tank #5:

  • week #2:
    • A.pedicellata: most growth tips extremely deformed, but some leaves appear to be healthy; older leaves turning brown
    • P.deccanensis: relatively fast, healthy growth; older leaves turning brown (dying)
    • R.wallichii: relatively fast growth, but poor condition (longer internodes and deformed growth tips)
    • H.corymbosa: fast growth, nice rich colors (orange-red at the top), but slightly wavy/twisted leaves
  • week #3:
    • A.pedicellata: a few stems rotted, but this did not affect the tips
    • P.deccanensis: relatively fast growth, good condition
    • R.wallichii: looks terrible
    • H.corymbosa: one pot removed so that the plant does not take up so much space in the aquarium; rich colors, fast growth, but compared to plants grown in soil, it has more wavy (slightly deformed) leaves
  • week #4:
    • A.pedicellata: more rotten stems; only a few stems and tops remain, which look more or less okay
    • P.deccanensis: good growth and good condition
    • R.wallichii: fast growth, but poor condition (looks terrible)
    • H.corymbosa: grew to the surface (harvest); fast growth, rich colors, but slight deformities
  • week #5:
    • A.pedicellata: kaput
    • P.deccanensis: good growth and condition; lush root system
    • R.wallichii: fast growth, but consistently poor condition (looks terrible); practically no roots
    • H.corymbosa: harvested
  • week #6:
    • A.pedicellata: ---
    • P.deccanensis: good growth/condition
    • R.wallichii: rapid growth, poor condition
    • H.corymbosa: ---
  • week #7:
    • A.pedicellata: ---
    • P.deccanensis: no change
    • R.wallichii: no change
    • H.corymbosa: ---
    • green water, algae/cyanobacteria growth

• Tank #6:

  • week #2:
    • A.pedicellata: very slow growth, older leaves turning brown (dying)
    • P.deccanensis: stagnant, older leaves turning brown (dying), new leaves not growing
    • R.wallichii: slow growth, but condition seems to be good in about half of the stems (upper leaves are straight, undistorted, and well colored), worse in the other half
    • H.corymbosa: slow growth, older leaves suffer from severe chlorosis (they are pale, some even white); all leaves (new and old): wavy/twisted, partially deformed
  • week #3:
    • A.pedicellata: stagnation, rotting stems
    • P.deccanensis: stagnation
    • R.wallichii: slow growth, condition varies (but more or less okay)
    • H.corymbosa: slow growth, chlorosis, some leaves slightly twisted
  • week #4:
    • A.pedicellata: completely rotted
    • P.deccanensis: very slow growth
    • R.wallichii: rather stagnant, condition not great
    • H.corymbosa: slow growth, deformation, chlorosis
  • week #5:
    • A.pedicellata: kaput
    • P.deccanensis: removed
    • R.wallichii: kaput
    • H.corymbosa: slow growth, deformation, chlorosis; only a few shorter roots
  • week #6:
    • A.pedicellata: ---
    • P.deccanensis: ---
    • R.wallichii: ---
    • H.corymbosa: no change
  • week #7:
    • A.pedicellata: ---
    • P.deccanensis: ---
    • R.wallichii: ---
    • H.corymbosa: no change, cyanobacteria growth (largest cyanobacteria invasion in this aquarium)

• Tank #7:

  • week #2:
    • A.pedicellata: a bunch of new leaves (nice color, but a bit wavy/twisted); it seems like the older leaves in this tank are turning brown the least
    • P.deccanensis: older leaves are turning brown (dying), new leaves at the top
    • R.wallichii: unrivalled best quality and fastest growth (!), longest leaves (!)
    • H.corymbosa: fast growth, nice rich colors (orange-red at the top), but twisted leaves
  • week #3:
    • A.pedicellata: compared to last week, I would say that its condition has deteriorated somewhat (as if it has stopped growing)
    • P.deccanensis: growing, but very slowly
    • R.wallichii: in the best condition, has grown to the surface (so I am harvesting it)
    • H.corymbosa: one pot removed so that the plant does not take up so much space in the aquarium; rich colors, fast growth, but wavy/twisted leaves
  • week #4:
    • A.pedicellata: ---
    • P.deccanensis: ---
    • R.wallichii: has grown to the surface (harvested)
    • H.corymbosa: has grown to the surface (harvested)
  • week #5:
    • A.pedicellata: growing, condition is relatively good, but not optimal (however, the lower leaves do not turn brown and decompose as much as in other aquariums)
    • P.deccanensis: complete stagnation (probably the worst condition of all)
    • R.wallichii: best condition of all (harvested)
    • H.corymbosa: rapid growth, rich colors, but deformation (harvested)
  • week #6:
    • A.pedicellata: passable (but not optimal) condition, slight deformation; rather small, but [apparently] healthy root system
    • P.deccanensis: removed
    • R.wallichii: ---
    • H.corymbosa: ---
  • week #7:
    • A.pedicellata: no change; roots more at the top (side) than at the bottom; new growth quite good, only with slightly deformed leaves; one shoot more (significantly) deformed
    • P.deccanensis: ---
    • R.wallichii: ---
    • H.corymbosa: ---

• Tank #8:

  • week #2:
    • A.pedicellata: stagnant (no signs of growth), older leaves turning brown
    • P.deccanensis: stagnant, older leaves turning brown (dying), new ones not growing
    • R.wallichii: excellent condition (only smaller than in aquarium #7), some growth tips appear to be slightly deformed, but this does not seem to affect further growth
    • H.corymbosa: growing (producing new leaves), but older leaves suffer from severe chlorosis (they are pale, some even white); all leaves appear to be wavy/twisted and partially deformed
  • week #3:
    • A.pedicellata: stagnation (no growth)
    • P.deccanensis: stagnation (no growth)
    • R.wallichii: good condition (moderately fast growth, good condition and color, no deformities)
    • H.corymbosa: slow growth, wavy/twisted leaves, chlorosis
  • week #4:
    • A.pedicellata: complete stagnation (slow dying)
    • P.deccanensis: complete stagnation (slow dying)
    • R.wallichii: mostly good condition (moderately fast growth), but a few (minority!) stems have slightly deformed growth tips
    • H.corymbosa: slow growth, deformation, chlorosis
  • week #5:
    • A.pedicellata: slight improvement => very slow growth, fairly good condition
    • P.deccanensis: removed
    • R.wallichii: overall very good condition (except for a few stems showing slight deformation of growth tips); virtually no roots
    • H.corymbosa: slow growth, deformation, chlorosis; lower leaves falling off; practically no roots
  • week #6:
    • A.pedicellata: fairly good condition, but very slow growth
    • P.deccanensis: ---
    • R.wallichii: no change
    • H.corymbosa: no change
  • week #7:
    • A.pedicellata: no change
    • P.deccanensis: ---
    • R.wallichii: no change
    • H.corymbosa: no change

Note: In the first weeks a brown haze was visible in the first experimental set (from leached humic substances from freshly flooded substrate).

Subjective assessment

Objective data

Legend:

%

ppm

State

C

N

P

K

Ca

Mg

S

Na

Cl

Fe

Mn

B

Zn

Cu

Mo

Deficiency

less than normal

Sufficiency

35-45

2-4

0.2-0.7

1-3

0.5-2.0

0.1-0.5

0.15-0.5

?

0.05-0.3

75-400

20-300

10-50

20-100

2-20

0.2-10

Excess

slightly more than normal

Toxicity

significantly more than normal

Notes:

• The ranges of deficiency, sufficiency (normal), and excess (toxicity) were taken from data applicable to terrestrial plants and adapted for aquatic plants using artificial intelligence (taking into account their physiological differences). However, I would like to point out that there is not any definitive standard (norm) for freshwater aquatic plants, so all I can offer is but a qualified estimate. I leave it up to the reader to evaluate and interpret this data in their own way.
• Where I had sufficient new material available, I used only this new material for analysis. In exceptional cases (e.g., Ammannia), I also used some of the old material (i.e., original leaves/stems). However, I never used roots.

Ammannia pedicellata 'Gold'

5.7 → (14)-5-20-6 mg/ℓ (Na):K:Ca:Mg, 20-2 mg/ℓ NO₃:PO₄, 200:100 µg/ℓ Fe:Mn + 10 mg/ℓ CO₂ + KH=2

	%							ppm
Tank	C	N	P	K	Ca	Mg	Na	Fe	Mn	Zn	Cu
5.7	41.76	4.11	0.77	2.40	1.56	0.61	1.41	1014	60	126	20

Rotala wallichii

5.5 → (14)-5-20-6 mg/ℓ (Na):K:Ca:Mg, 20-2 mg/ℓ NO₃:PO₄, 200:100 µg/ℓ Fe:Mn + 10 mg/ℓ CO₂ + KH=2

5.7 → (14)-5-20-6 mg/ℓ (Na):K:Ca:Mg, 20-2 mg/ℓ NO₃:PO₄, 200:100 µg/ℓ Fe:Mn + 10 mg/ℓ CO₂ + KH=0

	%							ppm
Tank	C	N	P	K	Ca	Mg	Na	Fe	Mn	Zn	Cu
5.5	41.15	4.14	0.76	1.94	1.82	0.55	2.46	3721	257	109	14
5.7	42.37	3.71	0.71	2.08	1.11	0.29	3.27	498	33	104	26

Hygrophila corymbosa

5.5 → (14)-5-20-6 mg/ℓ (Na):K:Ca:Mg, 20-2 mg/ℓ NO₃:PO₄, 200:100 µg/ℓ Fe:Mn + 10 mg/ℓ CO₂ + KH=2

5.7 → (14)-5-20-6 mg/ℓ (Na):K:Ca:Mg, 20-2 mg/ℓ NO₃:PO₄, 200:100 µg/ℓ Fe:Mn + 10 mg/ℓ CO₂ + KH=0

	%							ppm
Tank	C	N	P	K	Ca	Mg	Na	Fe	Mn	Zn	Cu
5.5	36.51	4.53	0.40	0.06 ?	4.58	0.74	0.46	146	76	206	13
5.7	40.28	4.73	0.42	0.06 ?	2.27	0.51	0.42	201	52	115	24

^? = Questionable result (error)

Pogostemon deccanensis

<n/a>

See the next experiment …