# Potting soil, co2, crypts and no ferts



## DHenry (29 May 2011)

Hello,

About 6 months ago I setup a small 16l tank using the walstad method. I started with potting soil capped with gravel and planted densely with crypts. No ferts, no co2, 3w of HO LED and no water changes. The tank is a resounding success. No algae at all. And the crypts are bright green and healthy. My high tech on the other hand has not been so easy. Nothing terrible but a few spots of algae and not all the plants are totally happy.

I have been thinking about re-scaping the high tech tank as per the little one with soil, low light, crypts etc. Then I got to thinking would it be at all beneficial to use the same method (walstad) only keeping the pressurized co2? Maybe at a lower level but not dose the water column with ferts. Will there be any benefit if the light is still low? I don't want to speed up growth necessarily because I know if I do then the tank will use up the nutrients in the soil quicker but I would still like to have a carpeting plant which I feel would be difficult without co2.

Any thoughts would be appreciated.


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## ceg4048 (30 May 2011)

Hi mate,
              No mileage in this plan. CO2 makes all the difference in the world. CO2 is what makes plants need more nutrition and light makes them use the nutrition faster. There is a fundamental difference between CO2 and non-CO2 which means you cannot mix the two without serious issues. Adding CO2 automatically means using more nutrients, no two ways about it. If you keep both lighting and CO2 at the very lower limits then that just means you can use a lower dosing regime or you might be able to get away with it by enriching the sediment with Osmocote or similar.

Cheers,


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## DHenry (30 May 2011)

I thought as much. The crypts in my 16l walstad tank are fantastic. The most success I've had. The high tech tank is a lot of work and for less reward. It's a lot less stable and has never really thrived. I would like to convert it to a lower maintenance tank as I don't really want to invest more time and money into more circulation more ferts etc. I do think choice a plants is crucial. The crypts seem to do very well in soil with no co2 but I am sure plants like HC probably won't. I may then go for another crypt tank with no co2 and no dosing.

Just to clarify a little. In a high tech tank co2 and ferts are maxed out and the growth rate is relative to light intensity. It works because there are no deficiency in ferts or co2. If you wanted to save by reducing co2 and ferts and light you end up treading a very fine line because you are limiting what is available to the plants. So there is no real point going half way because you will probably just make a mess. 

Thanks for your input.


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## ceg4048 (30 May 2011)

Hi mate,
              Well you see, the following statement isn't strictly accurate:


			
				DHenry said:
			
		

> In a high tech tank co2 and ferts are maxed out and the growth rate is relative to light intensity.


The problem with this statement is that one never needs to max out CO2, nutrients and light in order to make things work. It isn't a matter of all or nothing. The reason people fail with high tech tanks is generally because they automatically assume that high tech means high light.

In the biochemical equation of plants the amount of light drives the requirement for the amount of CO2, which in turn, drives the requirement for nutrients. The flow of these parameters ultimately governs the rate of growth.

Light===>CO2>==>Nutrients=>Growth Rate=>Organic Waste.

In this respect there is no difference between a CO2 enriched tank and a non-enriched tank. So if I make the assumption that I need a lot of light and if I then dump massive amounts of energy into the tank the above equation is driven from the far left to the far right with no possibility of mediation. But look more closely at the equation. If I restrict the Light intensity to some nominal value and instead add more CO2, can you see that I will still drive the equation to the right? 

I can restrict the Light and CO2 but add more nutrients. That will also drive the equation to the right. This equation/relationship can be though of as a snowball rolling down hill. The further uphill I start, the more energy I will produce at the bottom. So if I start at the very top and add tons of light, then it's effects multiply at each successive stage (I've indicated that by the length of the arrows between stages.) Lots of light requires lots of CO2 which requires lots of nutrients which produces lots of growth which produces lots of organic waste.

So if I want to limit the growth rate and limit organic waste production, the most logical path is to limit the light because it's the furthest uphill and it's effects are most prominent. In a low tech tank, by definition, the CO2 is severely restricted. Everything downstream is likewise severely restricted. Everything upstream must also be severely restricted, otherwise the system is broken. In your non-CO2 tank. since the light and CO2 are limited the requirement for nutrients are also limited. That's why you can get by on the restricted nutrient levels. There is no need to enhance the nutrients further. In this tank therefore, everything happens slowly. Growth is slow and organic waste production is slow, meaning that maintenance requirements are limited.

In your high tech tank, even if your light is not as intense as some others the injected CO2 results in a metabolism increase of somewhere between 3X to 10X of that present in the non-enriched tank. This places an enormous burden on the plants to uptake nutrients and CO2. That's why the other environmental factors all of a sudden become more critical. Flow becomes critical because it has a significant effect on the plants ability to pull CO2 from the water. Distribution techniques become critical because of the hydrodynamic limitations imposed by the water itself on the ability of nutrients and CO2 to keep in contact with the leaves. Organic waste buildup is so much faster that it pollutes the water and has the effect of blocking CO2 and nutrient uptake. That's why you need to change the water more often and to clean the plants to remove the waste buildup on the surface of the leaves. You need every trick in the book to give the plants a chance to maintain the CO2 and nutrient uptake rate in order to support their health.

In a high tech tank you can actually lower the growth rates by limiting the light, limiting the CO2 and by having good distribution methods to avoid inducing uptake failures. There is a wide range of Light/CO2/Nutrient combinations that will produce good results. There is no need to max everything out.

Hope this clarifies.

Cheers,


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## niru (30 May 2011)

ceg4048 said:
			
		

> In your high tech tank, even if your light is not as intense as some others the injected CO2 results in a metabolism increase of somewhere between 3X to 10X of that present in the non-enriched tank. This places an enormous burden on the plants to uptake nutrients and CO2. That's why the other environmental factors all of a sudden become more critical. Flow becomes critical because it has a significant effect on the plants ability to pull CO2 from the water. Distribution techniques become critical because of the hydrodynamic limitations imposed by the water itself on the ability of nutrients and CO2 to keep in contact with the leaves. Organic waste buildup is so much faster that it pollutes the water and has the effect of blocking CO2 and nutrient uptake. That's why you need to change the water more often and to clean the plants to remove the waste buildup on the surface of the leaves. You need every trick in the book to give the plants a chance to maintain the CO2 and nutrient uptake rate in order to support their health.
> 
> In a high tech tank you can actually lower the growth rates by limiting the light, limiting the CO2 and by having good distribution methods to avoid inducing uptake failures. There is a wide range of Light/CO2/Nutrient combinations that will produce good results. There is no need to max everything out.
> Cheers,



Hi Clive

thats a great re-read of the basics! 2 questions, at the risk of hijacking the thread (apologies for this): 

1. Given a high light, CO2 tank, if one 1st lowers the light (period & intensity) keeping the CO2 and ferts same as before, then did I get it correct that the plants are kind of compelled to utilize these to the fullest available for that reduced light (as you mentioned above) ? And why exactly is this? (Something like putting tempting food in front even if theres not much appetite gets vulnerable souls to over eat   ??) Of course going the other way is real no-no (low CO2, ferts but high light), but why is low light and more than needed fert/CO2 also equally (??) bad?

2. If one wants to "convert" a working high light+CO2+fert tank into a low tech tank so as to minimise organic waste buildup, whats the best strategy and over what timescale, so as to ensure minimal algae issues and plant deterioration?

-niru


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## DHenry (30 May 2011)

Thanks for the great information again Ceg,

I was posting quickly from my phone so I did over simplify. I was referring more to the establishment of a tank where you may start with more co2 and ferts than needed and reduce them to the point where you have good results in relation to the given light level. Anyway, your comment about having low light and higher co2 and the co2 still driving growth and nutrient uptake was interesting. I don't think I understood that fully before.

So in theory one could have a low light tank with low co2 and low nutrients but a reckon it would be a hard balance to find. I have had good success with no co2 so I may try this again on my larger tank.


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## ceg4048 (31 May 2011)

DHenry said:
			
		

> ...So in theory one could have a low light tank with low co2 and low nutrients but a reckon it would be a hard balance to find...


No mate, this is much easier to accomplish than trying to max everything out, although it's certainly more difficult than a non-enriched tank. As I mentioned before, the reason people have so much difficulty with high tech tanks is because they automatically assume that they need high light. How many times have you seen people post, where they buy a tank set with hood and lights, and the very first question they ask is how to add more light, or how to upgrade from T8 to T5 because they assume that the lights that came with the tank are not strong enough? I see a question like this almost every day. If the poster merely improved his/her flow rate and concentrated more on the rest of the equation they wouldn't have nearly as much difficulty. One can use low tech lighting and high tech everything else and the chances of success are much higher. When you tell them this their response is inevitably "Oh but I want to grow demanding, high light plants". The real answer is that there are no such things as high light demanding plants. Someone simply coined the phrase and suddenly it became "fact". You can find this bogus phrase listed in almost every plant catalog and uttered by almost every plant supplier, even by people who should know better.



			
				niru said:
			
		

> 1. Given a high light, CO2 tank, if one 1st lowers the light (period & intensity) keeping the CO2 and ferts same as before, then did I get it correct that the plants are kind of compelled to utilize these to the fullest available for that reduced light (as you mentioned above) ? And why exactly is this? (Something like putting tempting food in front even if theres not much appetite gets vulnerable souls to over eat   ??) Of course going the other way is real no-no (low CO2, ferts but high light), but why is low light and more than needed fert/CO2 also equally (??) bad?


Hi niru,
   Well, all organisms are programed for success. Whatever is available to them they will take. If you keep feeding your dog he/she will keep eating and will keep growing. This is the only way an acorn becomes an Oak. Since a plant will continue to grow until it dies for whatever reason (predation, disease, trauma) it will always attempt to maximize it's uptake of nutrients and CO2. If more CO2 becomes available, the plant will utilize it. The only thing that will slow the CO2 uptake, at any light level, will be the physical and chemical limitation of the uptake mechanism itself. At some point, adding more CO2 does not result in any additional growth rate increase simply because the physical limits of the movement of CO2 across cell boundaries and the physical limits of the speed of it's transport and use. From the plants perspective, at a given light energy level, the point at which adding more CO2 does not result in improvement is referred to as "unlimited CO2". It doesn't actually mean that there is an infinite supply of CO2 (because of course that's impossible) but from the plants perspective, it can't use any more so this is the same as having an unlimited supply. This is exactly the same with nutrients. For a given lighting level and CO2 level you can continue to increase the nutrient loading until a point is reached where adding more nutrients does not result in an increase in growth rate. The tank is then "nutrient unlimited". This is the principle of EI by the way.

Light energizes the plant uptake mechanism, therefore, increasing the light will enable a high value for the "unlimited" CO2 and a higher value for the "unlimited" nutrients. At some point adding more light does not result in increased ability to uptake more CO2 and nutrients, so this is light unlimited.



			
				niru said:
			
		

> 2. If one wants to "convert" a working high light+CO2+fert tank into a low tech tank so as to minimise organic waste buildup, whats the best strategy and over what timescale, so as to ensure minimal algae issues and plant deterioration


The answer is easy. Look at the equation. All you have to do is to lower the light intensity, wait a few weeks, then lower the CO2, then wait a few weeks, then lower the nutrient loading, then wait a few weeks, then repeat the cycle.

Obviously, the higher your starting point the more difficult and the longer the time required to pull this off without any difficulty. Another, more extreme strategy is to perform a blackout, or to just shut all the lights off and to shut the CO2 off. After 3 or 4 days without light and CO2 we can then resume the new low lighting level with reduced nutrient dosing and non-CO2. The response of the tank depends on a lot of factors such as temperature and species. Lowering the temperature by a few degrees helps lower the demand for CO2 & nutrients. The main factor, naturally is what the final lighting levels is.

Cheers,


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## nayr88 (31 May 2011)

Good read this,

I had a go at the soil style tanks once, went well. I used soil in from my garden  haha, would be cool to see some pictures of this crypt tank mate

Cheers


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## niru (31 May 2011)

ceg4048 said:
			
		

> niru said:
> 
> 
> 
> ...



Hi Ceg

I thought so... I am off for a 3 week vacation in a months time & have started implementing this process already for my tank. Currently the lights are on for 6 hrs, removed their reflectors. CO2 and EI ferts are at par. Next week I reduce light time further and later reduce CO2 from abt 4 bps to 2-3 bps and give EI at 2X per week instead of current 3X. So on and so forth. I finally plan to remove 1 T5 tube (i have 2 at 90W for 180 litre) and then switch off CO2 completely and "dilute" my EI dose with 2X freq. Lastly a few water changes by the time I go off! Hopefully the waste buildup is minimal and tank plants (& fish/shrimp) will cope properly. 

cheers
niru


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## DHenry (1 Jun 2011)

nayr88 said:
			
		

> Good read this,
> 
> I had a go at the soil style tanks once, went well. I used soil in from my garden  haha, would be cool to see some pictures of this crypt tank mate
> 
> Cheers


I've uploaded new photos to my journal. Check it out.


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## Victor (5 Feb 2014)

ceg4048 said:


> Light===>CO2>==>Nutrients=>Growth Rate=>Organic Waste. In this respect there is no difference between a CO2 enriched tank and a non-enriched tank. So if I make the assumption that I need a lot of light and if I then dump massive amounts of energy into the tank the above equation is driven from the far left to the far right with no possibility of mediation. But look more closely at the equation. If I restrict the Light intensity to some nominal value and instead add more CO2, can you see that I will still drive the equation to the right? I can restrict the Light and CO2 but add more nutrients. That will also drive the equation to the right. This equation/relationship can be though of as a snowball rolling down hill. The further uphill I start, the more energy I will produce at the bottom. So if I start at the very top and add tons of light, then it's effects multiply at each successive stage (I've indicated that by the length of the arrows between stages.) Lots of light requires lots of CO2 which requires lots of nutrients which produces lots of growth which produces lots of organic waste.


 So, I need to have more avaliable nutrientes than CO2 and more CO2 than light? Is that? Thank you, Ceg.


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