# Co2, nutrients & lighting - balance?



## phillyguy (Dec 30, 2011)

Since the goal is to have lighting, nutrients & co2 in balance, what are signs of various imbalances:

Light = L
Nutrients = N
Co2 = C

So there are 6 ways to be out of balance:
L - H H H L L L
N - H H H L L L 
C - L L L H H H 

So in above each column H = too high & L = too high.

The question in trying to be in balance, what would one observe under each of above out of balance scenarios?

I.e. column 1 lighting high, nutrients high, co2 low.

Make sense?

Thanks for anyone who can answer!


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## freph (Apr 4, 2011)

phillyguy said:


> Since the goal is to have lighting, nutrients & co2 in balance, what are signs of various imbalances:
> 
> Light = L
> Nutrients = N
> ...


Left side would generally be algae mecca. Not sure about the right side...


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## ecotanker (Jul 11, 2009)

Do you mean to have this table:


Lights----- H H H L H L L L
Nutrients- H H L H L H L L
CO2------- H L H H L L H L 

with H = too high, L = too low

I ask since the first three columns of your table are the same and so are the last three columns.


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## DarkCobra (Jun 22, 2004)

Your chart only displays two combinations, repeated three times.

But it's easier to state things in a different way.

1) The more light there is, the more nutrients and carbon plants need.
2) If nutrients or carbon are limited and not present in sufficient quantities, it harms plants.
3) If nutrients or carbon are present in the water column at sufficient quantities, but circulation is poor, it cannot reach the plants; so #2 still applies unless the substrate supplies the balance.
4) At high light, any limitation causes _far_ more harm than at low light.
5) Extremes of insufficient or excessive light, or grossly excessive nutrients, also harm plants.
6) If plants are present in sufficient quantity, and growing fast and healthy enough, they consume all the decaying matter that algae would otherwise induce and feed algae.
7) If a plant is unhealthy, it starts to decay, and _becomes_ food for algae.

That covers everything.


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## Hoppy (Dec 24, 2005)

It isn't really a problem of balance. It is, instead, a problem of having the light be the driver of the plants growth, and the only limitation on how fast the plants grow. The latter requires that there be enough of every other plant need available at all times, so only the light is limiting the growth.

With low light, therefore slow plant growth, not much of any other plant need is required. Often, with low enough light, the fish and excess fish food, along with the substrate, provide enough of everything, so the light is the only limit on the plants growth.

At higher levels of light, the fish, fish food, and substrate can't provide enough of everything for the plants, so we have to provide it separately. We have to keep every single nutrient supplied in large enough concentrations so that the plants are still limited only by how much light we have.

With very high light, it becomes very, very difficult to keep enough carbon available to the plants, and carbon becomes what limits the plants growth rate. This is bad, usually leading to unhealthy plants and resulting algae problems.

With high light and erratic fertilizing, one or more of the basic NPK nutrients can be present in too limited a concentration, becoming what limits the plant growth rate. This is also bad, and can lead to unhealthy plants, with algae soon to follow.

None of the plant needs, other than light, can be in so high a concentration that the excess of that nutrient/need will cause harm. CO2, as a carbon source, can become toxic to the fish at too high a concentration, but that doesn't harm the plants. And, the other nutrients are usually supplied as chemical compounds called "salts", so it is possible to have such an oversupply of one of them as to lead to brackish water, which is harmful to most plants. That takes way more than normal dosing of fertilizers though.

So, none of this is a case of "balance", just of keeping the light intensity as the only limit on the plant growth rate.


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## Reepicheep (Mar 21, 2008)

As a correlating question, what if I have low light but dose nutrients and inject C02? Will the excess nutrients and C02 foster algae growth or do harm in a low light setup, assuming regular large water changes?


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## phillyguy (Dec 30, 2011)

@ ecotanker, yes I totally blew the chart. Yours are the 6 scenarios I was trying to identify.


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## Hoppy (Dec 24, 2005)

Reepicheep said:


> As a correlating question, what if I have low light but dose nutrients and inject C02? Will the excess nutrients and C02 foster algae growth or do harm in a low light setup, assuming regular large water changes?


If you have low light, but dose everything, including CO2, as if you have high light, you should see no problems, other than that over time the fertilizer salts can build up in the water, eventually giving you brackish water and killing the plants. A big water change every week or so will prevent this. But, you should not see algae problems caused by doing this.


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## Flear (Jul 10, 2013)

as i think about nutrient balances i'm reminded of a few things, ... there's more than 2 nutrients

different PH levels will lock up or restrict certain nutrients
absence or excess of certain nutrients will restrict or lock up other nutrients.

if memory is correct - bacteria will produce organic compounds that are usually water soluble. (if they have access to the water column)

---

plants will try to grow as fast as light allows photosynthesis to continue.

higher light levels require higher CO2 & higher Nutrients, ... although at this level CO2 is nothing other than a nutrient the plant uses for it's own consumption (for the carbon), then things just boil down to light and nutrients.

all plants have a minimum light value (different for each type of plant), below this the plant will die, above this the plants progressively requires more and more nutrients to be available to it. non-vascular plants require these nutrients in the water column. vascular plants, not so much a requirement but can benefit the plants requirements.

as light levels increase, as light duration increases, nutrient requirements also increase, ... we are in control of the plants metabolism, if nutrients are not sufficiently available (doesn't matter if they're present or not, they have to be available to the plants), if they're not sufficiently available the plant will starve.

if certain nutrients are not sufficiently available to the plants (regardless of if they're present or not), then once again the plants health will be jeopardized.

---

now there's a lot of nutrients, not quantity, but different nutrients, potassium, phosphorous, carbon, iron, magnesium, boron, ... a whole bunch of others that i don't remember by heart.

you can have lots of nutrients, but if one is missing or restricted for whatever reason, ... it honestly does not matter about the rest does it ?


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