# Do We Definitely Need CO2?



## Dave Spencer (24 Apr 2009)

I have been lead to believe that CO2 injection is a must, but I originally started thinking about propogation and assumed a steady flow of air would supply this.

Anyway, the propogation unit I intend buying has a small sump with a pump and sprinkler system that sprays the roots, and keeps the humidity in the unit up. Will injecting the CO2 in to the water, and allowing it to be dispersed via the spray bar be a good idea?

Lighting will be via 11W Arc Pods, of which I have three. I`m not sure how many I will need. The problem will be how to mount them.

Space is at a premium, so I may have to go down the DIY CO2 route until I move house. 

So, the big questions are:

Do I keep the water dosed to EI levels?

Are there any other nutrients I need?

Dave.


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## GreenNeedle (24 Apr 2009)

Dave - Not sure I understand the CO2 question.  The plants are exposed to the air which means there are many many x more CO2 available to the plant naturally in the air than under the water @ '30ppm'



> I have been lead to believe that CO2 injection is a must, but I originally started thinking about propogation and assumed a steady flow of air would supply this.
> 
> Anyway, the propogation unit I intend buying has a small sump with a pump and sprinkler system that sprays the roots, and keeps the humidity in the unit up. Will injecting the CO2 in to the water, and allowing it to be dispersed via the spray bar be a good idea?



I would assume that this would have a similar result to in tank conditions only amplified many times.  I wouldn't be surprised if the water when it hits the bottom of the tank is actually virtually back at equilibrium again.

I grow mine in propogators with lids to keep the humidity up and they are housed in my old tank cabinet with the doors closed which keeps the temp up too.

Each shelf has one full length flouro above it and each shelf currently has 90 x 5cm pots on it.  I will be moving this to around 130 per shelf soon.

Initially fill the tray with tank water at water change.  From then on I mist spray daily (if I remember) with a bottle containing old tank water.  Therefore it is basicaly EI as the water used is the 'end of week build up' from the tank.

I don't bother with water movement either.  The Air is obviously spread and the ferts distribution is via the spraying so its not a problem.  When I mist it lets in some fresh air so it won't get depleted.  The lids also have a couple of indentations where they meet the tray which lets a little air in and out.

I did look at ebb and flow systems etc but found that this cheapo way as long as temp and humidity is kept up well works perfectly. and is dead easy to take a tray out, work on the kitchen table and then replace etc 

So far this method is working with HC, Glosso, Anubias, Microsorum and I am currently experimenting with a few Crypts.

AC


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## Dave Spencer (24 Apr 2009)

SuperColey1 said:
			
		

> Dave - Not sure I understand the CO2 question.  The plants are exposed to the air which means there are many many x more CO2 available to the plant naturally in the air than under the water @ '30ppm'



This was exactly my line of thinking, Andy. Keep a steady flow of air through the unit and the plants will get more CO2 than they could ever need.

My thinking with the CO2 injection in to the water was that the gas would barely have time to dissolve in the water, so the spray bar would distribute the gas nicely throughout all the plants.

Keeping it simple certainly appeals to me Andy. Do you just keep the plants in inert sand?

Dave.


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## Fluidsensoronline (24 Apr 2009)

CO2 in the air runs about 300ppm in a grow room environment you'd probably want to aim for 1000-2000ppm
You could run the co2 in your nutes but there's not really any point imo, just release it top side where it's going to be used.
You might not want to bother at all with it if SC is getting good results. Opening the door and getting good air exchange is probably the key there. For me I might not get chance to open the lid for a day or week if i'm busy with the engineering side of my work. I run fans inside for airflow with few vents. Humidty @ 90%
You want as much O2 as possible around your roots (your aeroponic system checks that box)
As for EI levels of nutrients, I don't currently have figures but i'm running my solution at about 120ppm Nitrate. You don't have to worry about algae (that's almost true ) so you may as well dose high levels and lower the attention you need to pay. Funny you should use the term EI though, we're currently looking at the benefits of dumping 50% of the nute tank and "topping up" the nute levels  - EI style, as an alternative to dumping the full tank once the EC drops. This is made possible by using a recipe and individual ferts like calcium nitrate as opposed to buying off the shelf products
Lighting - as much as possible for me, and that includes getting it as close as possible without scorching risk.

Thing to do is jump in and try it, see what works........

Nigel


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## Steve Smith (27 Apr 2009)

I've seen a grow unit where groups of plants are in plastic containers, with clear lids, and CO2 fed straight into the containers, giving a pocket of CO2 trapped in the container.  No fancy diffusers or anything, just tubing into the container.  Seemed to be working very well


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## LondonDragon (27 Apr 2009)

What about using a mist sprinkler in a tank of some sort with a lid that has holes to let in some air and the plants would grow emersed but remain always wet and plenty of CO2 in the air for them???


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## Dan Crawford (27 Apr 2009)

LondonDragon said:
			
		

> What about using a mist sprinkler in a tank of some sort with a lid that has holes to let in some air and the plants would grow emersed but remain always wet and plenty of CO2 in the air for them???


This is what i intend to do, i have an exo-terra fogger and it's really quite efficient.
http://www.exo-terra.com/en/products/fogger.php


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## vauxhallmark (27 Apr 2009)

Won't that dramatically reduce light? Or will it just come on occasionally on a timer?

Mark


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## Dan Crawford (27 Apr 2009)

I should have made it a bit clearer, sorry. I'll be running this underneath to just keep the roots moist and it _should_ keep the humidity up


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## GreenNeedle (27 Apr 2009)

There's a flip side to this.

If you are doing the emersed in tank style setup with substrate then it is harder to keep humidity up.  If you have potted plants placed in open water the humidity is pretty impressive.

I suppose you could just try placing a bowl of water (however small) somewhere that you aren't planting the emersed plants and that would do a similar thing 

I'll stick to my cheapo setup though.  Is working great .  I will be up to the 200+ pots pretty soon   Then going to try it in the mini greenhouse from June to see if I can push on to 500+ 

AC

AC


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## Dan Crawford (27 Apr 2009)

Heres a quick sketch of what i'll be attempting.....


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## GreenNeedle (27 Apr 2009)

some people just like to spend money 

AC


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## vauxhallmark (27 Apr 2009)

Why don't you want the roots in the water? 

Mark


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## Fluidsensoronline (27 Apr 2009)

vauxhallmark said:
			
		

> Why don't you want the roots in the water?
> 
> Mark



To try and get as much Oxygen to them as possible, it's done in different ways with different techniques. Fog, airstone, spray etc.
Currently I'm running the water back into my sump with a waterfall effect and dropping the water in the plant bay completely once every 3 hours (like a modified flood drain system) but my roots are submerged in that oxygenated water for 165mins of the 3 hrs....


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## Dan Crawford (27 Apr 2009)

SuperColey1 said:
			
		

> some people just like to spend money
> 
> AC


   I've got all the stuff mate, i won't cost me a bean  I'll even make the perspex lid myself with free materials from work


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## plantbrain (27 Apr 2009)

The question might be do we "need" to add CO2 enrichment?

Obviously no.

Does it increase plant growth under water?
5-20X, maybe more.

Why?

The rate of CO2 exchange is 10,000x slower under water, so the CO2 cannot get to the plant and supply the same demands as the gas above water does.

This is why aquatic plants are generally CO2 limited, not nutrient limited in most situations in nature.
I'd say it's also true for aquariums for that matter

I find serious issue with people that demand that methods limit nutrients, but then add lots of light and CO2.

If you go with the concept and logic that we should use "less is better", then this should apply to all 3 basic parameters for growth, not just one   So you would use less light(cost less better for CO2 footprint, runs the tank more efficently, and we do not "need" high wasteful light either), you would not use CO2 at all, or perhaps Excel instead.......if you want more species choices, and then...........finally............you will dose less nutrients, say sediment ferts and fish waste..........and no water changes/testing.

It can be done and can look nice.
Some claim you do not need 30ppm of NO3........well........since I wish to cut corners/use less.........let's see how much of a hypocrite I might be.

It's harder, takes more patience and skill, but can be done.

So why add CO2, more light and nutrients?
You want higher rates of growth.

Aeration alone cannot add enough CO2 to meet the demand for submersed plants, even at higher currents.
You still have that 10,000 slower exchange rate. To deal with that, we add 10X more concentration which seems to help and increases the rates of growth about 10X as well.

It's also why 99% of the aquatic plants are grown above water and no algae.

Regards, 
Tom Barr


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## altaaffe (27 Apr 2009)

I don't see why you would need the CO2 injection if the plants are being grown emersed.  They should be able to get all the CO2 they want from the air if they are grown emersed as long as it's not an air tight seal being put on it.  

I have been growing plants emersed now with just the water from a main tank, the humidity will be at a reasonably high level (looking at the amount of condensation I get on the covers).

viewtopic.php?f=56&t=5903

I have the roots submersed here though


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## GreenNeedle (27 Apr 2009)

Did I read Tropica toyed with the idea of injecting CO2 and not go with it?

AC


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## Dave Spencer (27 Apr 2009)

Well, my mind is made up after seeing Andy`s neat set up. Atmospheric CO2 is the way ahead for me, and hope I don`t need to inject any.

Dave.


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