Chapter 1: Growing plants with heavy fertilisation in the water column
Introduction
Plants differ not only in shape, color, size or growth rate, but also in their requirements or preferences. While all plants need water, light, heat, nutrients and the absence of harmful influences to grow well, some need to have these mixed in a specific ratio. In a way, it's similar to humans: while some people are not too picky about food (they'll eat anything), gourmets are picky eaters (they despise ordinary food). Similarly, some plants will grow in almost any circumstances (in acidic or alkaline water, in low or high light, in sand or organic soil, in nutrient-poor or nutrient-rich water), while others are a little more "spoiled" and therefore require more specific environmental parameters (whether it concerns the intensity of the light, the physico-chemical parameters of the water, or the composition and characteristics of the substrate). Figuring out what each plant prefers (or downright requires) is not easy. First of all, it requires us to identify all the relevant factors that play a significant role → e.g. pH, redox, organic compounds, light intensity, temperature, content and ratio of different nutrients, substrate properties, microbial composition, etc. These factors then need to be tested in order to clarify the extent to which they influence the outcome - i.e. the growth and condition of our plants. This experiment is an attempt to test a particular set of factors that I have identified as potentially important. [I am by no means claiming that my selection is the most important or comprehensive. But I have to start somewhere.] In each of the eight aquariums, I used a different recipe (i.e., a different set of factors) in the hope of revealing the particular preferences of each [tested] plant. This experiment, however, is only a sort of "first chapter" in a series of other tests that I plan to carry out gradually. I believe, however, that it may provide valuable partial insights from which a more complete picture (mosaic) of our aquarium plants and their needs (preferences) can be assembled over time. More detailed information and further experiments can be found [if interested] on my website: golias.net/akvaristika/.
The main objective
To identify the optimal parameters for cultivation of aquarium plants.
Aquariums
Eight identical aquaria → 20 liters or 5 gallons (net volume) each
Plants
In this experiment I decided to use the following emersion plants (i.e. plants grown in a greenhouse):
Diagram of plant placement in individual aquariums ↓
Picture of the fifth aquarium (few days old) ↓
Picture of all eight experimental aquariums ↓
Light
Lighting interval: 8h/day
Light intensity (PAR) in individual aquariums:
Note: There was no difference between the values in the middle vs. at the corners of the aquarium on the horizontal axis (except for the top section = near the light source).
↑ Measured with Apogee MQ-610 (full-spectrum quantum meter). The measured values were [in accordance with the manufacturer's instructions] converted for an underwater environment using a correction factor of 1.25.
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
Because the organic substrate should contain sufficient N, P and micronutrients (NPµ), these nutrients were not added to the water column; I assumed that some N and P would be leached from the substrate into the water column anyway.
I used a local horticultural substrate for aquatic plants capped with a layer of silica sand.
In aquariums without substrate, I used M16 stainless steel hexagonal nuts inserted into small hydroponic net pots (Ø 5 cm = 2") to anchor the plants. The stems in the nuts were held in place by a small strip of coarse foam.
Water
Note: The recipes below were prepared using pure (demineralized/deionized) reverse osmosis water.
Documentation
planting: 2024-10-04
week #1: 2024-10-12
week #2: 2024-10-19
week #3: 2024-10-26
week #4: 2024-11-02
Details (first experimental set: aquaria #1 to #4):
Details (second experimental set: aquaria #5 to #8):
week #5: 2024-11-09
week #6: 2024-11-16
week #7: 2024-11-23
Results
Note: In the first weeks a brown haze was visible in the first experimental set (from leached humic substances from freshly flooded substrate).
The following data is a brief description of the visual condition of the plants in each aquarium (1 to 8). Green indicates best condition, blue indicates good condition and red indicates fair condition.
The pH values below represent the average measured in the last weeks of the experiment.
Ammannia pedicellata 'Gold'
Hygrophila corymbose
Pogostemon deccanensis
Rotala wallichii
Evaluation
Keep in mind that:
Ammannia pedicellata 'Gold'
Probable characteristics:
Hygrophila corymbosa
Probable characteristics:
Pogostemon deccanensis
Note: The purchased plants were not in the best condition, so their onset was considerably delayed (they started to show some growth only from about the third week). Also, this plant [appears] to show no marked signs of deficiency and is therefore not a suitable indicator of malnutrition.
Probable characteristics:
Rotala wallichii
Probable characteristics:
Introduction
Plants differ not only in shape, color, size or growth rate, but also in their requirements or preferences. While all plants need water, light, heat, nutrients and the absence of harmful influences to grow well, some need to have these mixed in a specific ratio. In a way, it's similar to humans: while some people are not too picky about food (they'll eat anything), gourmets are picky eaters (they despise ordinary food). Similarly, some plants will grow in almost any circumstances (in acidic or alkaline water, in low or high light, in sand or organic soil, in nutrient-poor or nutrient-rich water), while others are a little more "spoiled" and therefore require more specific environmental parameters (whether it concerns the intensity of the light, the physico-chemical parameters of the water, or the composition and characteristics of the substrate). Figuring out what each plant prefers (or downright requires) is not easy. First of all, it requires us to identify all the relevant factors that play a significant role → e.g. pH, redox, organic compounds, light intensity, temperature, content and ratio of different nutrients, substrate properties, microbial composition, etc. These factors then need to be tested in order to clarify the extent to which they influence the outcome - i.e. the growth and condition of our plants. This experiment is an attempt to test a particular set of factors that I have identified as potentially important. [I am by no means claiming that my selection is the most important or comprehensive. But I have to start somewhere.] In each of the eight aquariums, I used a different recipe (i.e., a different set of factors) in the hope of revealing the particular preferences of each [tested] plant. This experiment, however, is only a sort of "first chapter" in a series of other tests that I plan to carry out gradually. I believe, however, that it may provide valuable partial insights from which a more complete picture (mosaic) of our aquarium plants and their needs (preferences) can be assembled over time. More detailed information and further experiments can be found [if interested] on my website: golias.net/akvaristika/.
The main objective
To identify the optimal parameters for cultivation of aquarium plants.
Aquariums
Eight identical aquaria → 20 liters or 5 gallons (net volume) each
Plants
In this experiment I decided to use the following emersion plants (i.e. plants grown in a greenhouse):
- Ammannia pedicellata 'Gold' (formerly known as Nesaea sp. Gold)
- Hygrophila corymbosa
- Pogostemon deccanensis (formerly known as P. erectus)
- Rotala wallichii
Diagram of plant placement in individual aquariums ↓
Picture of the fifth aquarium (few days old) ↓
Picture of all eight experimental aquariums ↓
Light
Lighting interval: 8h/day
Light intensity (PAR) in individual aquariums:
- top: 231 µM/m2·s → just below the water surface
- middle: 98 µM/m2·s
- bottom: 96 µM/m2·s → at the bottom
Note: There was no difference between the values in the middle vs. at the corners of the aquarium on the horizontal axis (except for the top section = near the light source).
↑ Measured with Apogee MQ-610 (full-spectrum quantum meter). The measured values were [in accordance with the manufacturer's instructions] converted for an underwater environment using a correction factor of 1.25.
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
Because the organic substrate should contain sufficient N, P and micronutrients (NPµ), these nutrients were not added to the water column; I assumed that some N and P would be leached from the substrate into the water column anyway.
I used a local horticultural substrate for aquatic plants capped with a layer of silica sand.
In aquariums without substrate, I used M16 stainless steel hexagonal nuts inserted into small hydroponic net pots (Ø 5 cm = 2") to anchor the plants. The stems in the nuts were held in place by a small strip of coarse foam.
Water
Note: The recipes below were prepared using pure (demineralized/deionized) reverse osmosis water.
- Water flowensured by a surface skimmer (Jingye JY-350)
- no filtration used
- Water changes done once a week (with 50% of the water changed) with macro-nutrients replenishment
- Micro-nutrients added every other day (most in the form of EDTA chelates, iron in the form of gluconate + DTPA)
- Extra CO2 added to aquaria #1, #3, #5 and #7 using a simple glass diffuser, the function and parameters of which are described in more detail in a separate article
- target CO2 concentration in these aquaria: ~15 ppm
- The pH fluctuated or decreased during the experiment (in some aquariums quite significantly) → see photo documentation for week #4.
Documentation
planting: 2024-10-04
week #1: 2024-10-12
week #2: 2024-10-19
week #3: 2024-10-26
week #4: 2024-11-02
Details (first experimental set: aquaria #1 to #4):
Details (second experimental set: aquaria #5 to #8):
week #5: 2024-11-09
week #6: 2024-11-16
week #7: 2024-11-23
Results
Note: In the first weeks a brown haze was visible in the first experimental set (from leached humic substances from freshly flooded substrate).
The following data is a brief description of the visual condition of the plants in each aquarium (1 to 8). Green indicates best condition, blue indicates good condition and red indicates fair condition.
The pH values below represent the average measured in the last weeks of the experiment.
Ammannia pedicellata 'Gold'
Hygrophila corymbose
Pogostemon deccanensis
Rotala wallichii
Evaluation
Keep in mind that:
- Higher light (more energy) = higher nutrient demand (especially CO2) = higher risk of deficiency
- In the first experimental set, NPμ is absent in the water column and plants there depend on NPμ in the sediment, which might have [negatively] affected the result (yield/condition) compared to the second experimental set → causing NPμ deficiency or heavy metal (or hydrogen sulphide) toxicity in the sediment
Ammannia pedicellata 'Gold'
Probable characteristics:
Hygrophila corymbosa
Probable characteristics:
Pogostemon deccanensis
Note: The purchased plants were not in the best condition, so their onset was considerably delayed (they started to show some growth only from about the third week). Also, this plant [appears] to show no marked signs of deficiency and is therefore not a suitable indicator of malnutrition.
Probable characteristics:
Rotala wallichii
Probable characteristics:
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