THE 2HR AQUARIST
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    • ABOUT
    • community
    • 2 Minute Bites
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  • Planted Tank Guide
    • AQUASCAPING IDEAS
    • PLANTED TANK 101
    • CHOOSING A TANK
    • CHOOSING A LIGHT
    • CHOOSING A CO2 SYSTEM
    • CHOOSING SUBSTRATE
    • CHOOSING FERTILIZERS
    • CHOOSING FILTERS
    • CHOOSING PLANTS
    • KEEPING LIVESTOCK
    • ALGAE CONTROL
    • WATER PARAMETERS
    • FAQ
  • Indepth Topics
    • CO2 FINE-TUNING
    • SUBSTRATE IN-DEPTH
    • LIGHT & LIGHTING OPTIMISATION
    • NUTRIENT DOSING
  • Plant Guides
    • Carpeting plants without CO2
    • Alternanthera reineckii
    • Blood vomit
    • Bucephalandra species
    • Cryptocoryne flamingo
    • Eriocaulon Quinquangulare
    • Hygrophila pinnatifida
    • Hygrophila sp. chai
    • HC 'Cuba'
    • Limnophila aromatica
    • Ludwigia arcuata
    • Rotala rotundifolia
  • Newsletters
    • ADA Visit
    • Red plants
    • Nutrient tunnel vision
    • How to reset a tank
  • buying guides
    • lighting
    • filters
    • co2 related
    • substrates
    • fertilisers
    • 2Hr Aquarist Fertilizer
      • Dealers
    • plants
    • algae control
    • water parameters
    • keeping livestock
  • HOME
    • ABOUT
    • community
    • 2 Minute Bites
    • April Giveaway
    • Help
  • Planted Tank Guide
    • AQUASCAPING IDEAS
    • PLANTED TANK 101
    • CHOOSING A TANK
    • CHOOSING A LIGHT
    • CHOOSING A CO2 SYSTEM
    • CHOOSING SUBSTRATE
    • CHOOSING FERTILIZERS
    • CHOOSING FILTERS
    • CHOOSING PLANTS
    • KEEPING LIVESTOCK
    • ALGAE CONTROL
    • WATER PARAMETERS
    • FAQ
  • Indepth Topics
    • CO2 FINE-TUNING
    • SUBSTRATE IN-DEPTH
    • LIGHT & LIGHTING OPTIMISATION
    • NUTRIENT DOSING
  • Plant Guides
    • Carpeting plants without CO2
    • Alternanthera reineckii
    • Blood vomit
    • Bucephalandra species
    • Cryptocoryne flamingo
    • Eriocaulon Quinquangulare
    • Hygrophila pinnatifida
    • Hygrophila sp. chai
    • HC 'Cuba'
    • Limnophila aromatica
    • Ludwigia arcuata
    • Rotala rotundifolia
  • Newsletters
    • ADA Visit
    • Red plants
    • Nutrient tunnel vision
    • How to reset a tank
  • buying guides
    • lighting
    • filters
    • co2 related
    • substrates
    • fertilisers
    • 2Hr Aquarist Fertilizer
      • Dealers
    • plants
    • algae control
    • water parameters
    • keeping livestock

FINE-TUNING CO2

THE 2HR AQUARIST'S GUIDE TO FINE-TUNING CO2 IN THE PLANTED AQUARIUM

PUSHING LIMITS
DISTRIBUTION METHODS
HOW TO MONITOR
LIGHT & CO2

HOW TO PAIR LIGHT WITH CO2

​THE RELATIONSHIP BETWEEN LIGHT & CO2

​A key question is, when there is no CO2 injection, and CO2 levels are low, does having higher light increase growth rates? The answer is yes, though the increase in growth is no where as much as when there is injected CO2. 
This is demonstrated in the experiment below by Andersen (1999) Interactions between light and inorganic carbon stimulate the growth of Riccia fluitans, University of Copenhagen.
Picture
​Figure (left) shows how 1 gram of Riccia develops over two weeks at given lighting and CO2 levels.
  • At low light, low CO2, Riccia barely grows and 1g grows into 1.16 grams after 2 weeks (white line).
  • At low light, high CO2, 1g grows into 1.75g (green line)
  • At high light, low CO2, 1g grows into 2.41g (blue line)
  • At high light, high CO2, 1g grows into 6.9g (red line)

Picture
​The other outcome of the experiment showed that the increase in growth rates when either CO2 or lighting was increased is subjected to diminishing returns. This means that when light or CO2 is lacking, small increments gave a big boost to growth, however, increasing from a medium to high level still gives a boost to growth, but in a marginally smaller way.

It also demonstrates, in a counter-intuitive way, that having high light even in low tech scenario does have a significant impact on growth. While this may cause more algae issues for unbalanced aquarium, I find that using high light on low tech tanks allow growing of more difficult species that usually don't adapt well to low tech conditions.

LIGHT IMPACT IN HIGH VS LOW CO2 ENVIRONMENT

Picture






The chart on the left compares photosynthesis in a tank with high CO2 vs low CO2.

When CO2 levels are low, photosynthesis levels are limited by low CO2 levels; thus the maximum amount of light that can be utilised is lower compared to that of a high tech planted tank. The photosynthesis curve thus taper off at a lower point compared to a tank with high levels of CO2 as light levels increase.
Picture
​However, plants can channel energy to different functions; a lack of nutrients for example, may cause the plant to dedicate more energy to root growth, a lack of light stimulates stem elongation and more energy in light absorbing pigments and chlorophyll. At low CO2 levels, plants invest more energy in enzyme production to aid CO2 uptake & fixation.

Therefore, the light compensation point (level of light at which net energy needs of the plant is met) is actually higher for low tech tanks compared to CO2 injected tanks. For the latter, CO2 is easy to attain so plants require less light to have surplus energy to grow. This gives rise to the odd combination that at the extreme end of low light, high tech tanks can survive with lower absolute light levels compared to low tech tanks, while being able also to utilize much higher lighting levels if given. High tech tanks operate within a much larger range then compared to low tech tanks; which cannot have too low light, nor make use of too high lighting. 

This is detailed in the chart on the side. The red line is the light compensation level of photosynthesis. Only above this level do we get net growth. Below this level, plants starve.

ADJUSTING LIGHT LEVELS IN TANKS

What does all this mean?

​This means that having more light in low tech tanks WILL improve growth rates, even though the marginal impact is smaller than compared to in a CO2 enriched tank. Using higher lighting in low tech tanks is one way to grow more difficult species that otherwise do very poorly in low CO2 environments. The main downside of using higher lighting is that one may face more algae issues. I use 100 Umols of PAR effectively in my low tech setups, but for those looking to growth plants not usually suitable for low tech tanks, I would recommend a range between 60-80 Umols at substrate level.

For high tech tanks, growth rates also eventually taper off as light levels are increased even with CO2 enrichment. There is little marginal gain to growth rates by increasing PAR beyond 600-800 umols.

​This is mainly theory crafting, as other than outdoor farm tanks receiving sunlight, most tanks will never get so much light. For outdoor farm tanks, having 6% - 70% shade cloth will cut down PAR from sunlight from 2000 to around 600-800 Umols. 
Picture
Using soil and higher lighting is one way to cheat past the limitations of low tech / non CO2 injected tanks. In this tank, the Monte carlo carpet grows in significantly over a 3 month period.

BACK TO...

PUSHING THE LIMITS OF CO2 SAFELY

  • How to enable higher CO2 injection rates without killing livestock.
  • The 3 factors that affect gaseous exchange.
  • 3 ways to improve gaseous exchange.
GO

THE 2HR AQUARIST GUIDE TO INJECTED CO2

why
​CO2?

Is it really necessary? What are the costs involved? Is it natural?
GO

system
101

What is the regulator? How do I set up a diffuser? What do they cost?
GO

diffusion
​basics

Which is better? Diffusers, inline Atomizers or Reactors. How do they work?
GO

tuning
​CO2

How do I start? How much to inject? For how long? What is too much?
GO

top
​myths

Does CO2 harm fish? Will my low light tank benefit from CO2?
GO

where
to buy

My recommendation on commercial choices.
GO
PUSHING LIMITS
DISTRIBUTION METHODS
HOW TO MONITOR
LIGHT & CO2

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