DIY co2 diffuser options

[davidjp1982]

Just looking for some advice regarding co2 diffuser options. I've been looking recently at the benefits of co2 in the planted aquarium and I can see I already have most of what I need to give it a go namely yeast, sugar, baking powder, bottles and standard airline tubing. I have a standard airstone would this be ok for a 15 gallon set up using a 2 litre bottle diy setup? Can I just use the airline direct without a stone? Do I need a second bottle setup to avoid any crud entering the tank? I see on the nutrafin diy kit you can buy they don't use a second bottle at all it just goes straight to their ladder diffuser system. Really appreciate any tips as it seems I am ready to set this up tonight if I have everything I need. Thanks

 

[davidjp1982]

Another option I was thinking about would be to insert the airline into a small cube of filter sponge to trap the bubbles and keep them in the water?

 

[regani]

You shouldn't need a second bottle if you don't overfill the reactor bottle (I do about 1/3 full) and keep the bottle above the water level in the tank. Some people prefer to use it but I have never had any issues with bottle.
A diffuser should make the bubbles as small as possible to maximise contact surface and CO2 dissolution, that is why an open tube is almost completely useless. A normal air stone is a little better but the bubble size is still fairly big and therefore overall contact area a bit small. A special CO2 atomiser does a much better job at this.
I would get one of those pipe-shaped CO2 diffusers with the porous glass frit on top. Short of an inline CO2 diffuser/mixer for a canister filter outlet they do the best job, IMO

 

[davidjp1982]

I've gone with a Swan cigarette filter in the end of the airline - I got the idea from here

- I've got an internal PF2 filter what I would like to do is direct the bubbles to be sucked into filter and dispersed. I've used a second bottle but will probably look at the state of the water in it after a couple of weeks and judge whether it's actually doing anything other than being 2 more potential leaks. Been set up for 2 hours now hopefuly by the morning I will see some action

 

[Josh]

I've done it both ways in the past - with and without a middle chamber to catch any debris. I definitely use a diffuser too. That's a neat video with some good ideas. Keep us updated on how your system works out for you. Would love to see some photos.

 

[davidjp1982]

Just to clarify - that wasn't my video it was just where I saw the idea for the filter diffuser. So far I haven't had enough pressure to diffuse into either an airstone or a filter unless I shake the bottle to produce about 5 bubbles a second - only an open tube produces any bubbles without agitation. I think my second bottle has a leak as I can smell yeast above the cap. Second bottle was just a water bottle not sure if this makes a difference as it isn't designed for fizzy drinks? Going to try a small lemonade bottle or similar later and see if I can get everything airtight. Will update with pics!

 

[themountain]

For a small tank >100 liter I would recommend this :http://de.wikipedia.org/wiki/Paffrathsche_Rinne
The Paffrathsche channel(also: Paffrathsche shell , Paffrathschale )
is a simple device to dissolve (CO2) carbon dioxide in water. Its origin and it most common use is in the aquarium, where it is used for supplying biologically produced ( by yeast fermentation ) CO2. It was named after its developer Kurt Paffrath , an aquarium author. CO2 acts as an important plant nutrient and also affects the pH of the aquarium water .
Principle of operation
An inverted cup , which is mounted, for example by means of suction cups below the water level in the aquarium. In the upwardly facing bottom are often one or two passages assembled , one of the CO2 supply is used and the possible second , provided with a short hose and a shut-off valve is used as a so-called waste gas vent to present in the shell of air , which is lighter than CO2, to let escape upwards .
Operation
The supply of CO2 from a fermentation vessel accumulates beneath the inverted bowl . At the contact surface of the resulting CO2 bubble to the aquarium water, the gas diffuses into the liquid. Due to different sizes selected shells there will be differently sized contact or diffusion areas . In this way you can adjust the amount of CO2 to be dissolved on the aquarium size.

Size calculation : Base size : 100 liters
Carbonate contact surfacein
KH up to cm ²
10 ---> 30
11 ---> 50
12 ---> 70
13 ---> 90
14 ---> 110
15 ---> 130
16 ---> 150
Advantages over conventional CO2 supply devices
Known adding devices (or called reactors) , such as pinball, diffusers or external reactors ( the initiation of CO2 in the water of the filter circuit ) continuously solve the supplied gas in the water. This addition is controlled by controlling the CO2 flow rate.This is in the known pressure bottle systems not a problem because the amount of gas can be set constant by means of a valve .
In biologically produced CO2 , however, the gas generation does not proceed uniformly , it is dependent on the temperature and also on the length of the fermentation process , there is also during production of the CO2 flow, the danger of explosion of the fermentation tank , which is normally only a plastic bottle or canister and is not suitable for high pressure. However, since the contact area of the CO2 to the water in the channel is always the same and there is a more or less uniform addition of the gas is ensured to the aquarium water. If more gas is supplied , as the shell can hold , it escapes just as a bubble on the lower edge of the shell .
Disadvantages compared to conventional CO2 supply devices
Due to the required contact area a Paffrathsche channel inside the aquarium is difficult to hide . The attachment can problematic due to the buoyancy of the gas-filled shell .

For me it worked always well

 

[davidjp1982]

Thanks that looks really good - I will look into that if I cant get a good level with my current set up. I managed to fix the leaks by replacing both caps with sprite caps which seen a bit thicker, I drilled a hole smaller than the tubing and pulled the airline through to self seal. I used a heated screwdriver to widen the end of the tubing to be able to fit a Swan cigarette filter in without having to compress it and it's working straight away - got it attached to internal filter with elastic band and set a deflector on the filter outlet facing downwards so it catches the bubbles and blows them about. Fingers crossed the seals will stay sound and I will see some results!

 

[davidjp1982]

One more question! I used to have an airstone running 24/7 but now I am running diy co2 I obviousley want to keep this turned off in the day to stop the co2 gassing off. Surface movement is close to none. I'm a bit worried about the fish suffering from lack of oxygen, I am sure I am just imagining it but I think they look to be breathing a bit faster than normal. Should I run the airstone at night? I am just as concerned that running an airstone at night will create ph swings by driving off the co2 at night and then boosting co2 in the morning by turning airstone off? Co2 is running 24/7 of course. Am I worrying about nothing?

 

[davidjp1982]

pH has dropped from 7.4 to anywhere between 6.6 to 7 in less than 3 hours (my eyes can't tell the difference on the colour chart). I'm a bit worried what will happen over night at this rate (its nearly 10pm).

 

[davidjp1982]

Using this chart my co2 is already nearing dangerous levels after 3 hours?? (kh is 5, ph was 7.4)

 

[regani]

It is highly unlikely to get to levels of CO2 dangerous for fish using DIY methods. As long as you don't have the top completely closed off so that there is no air exchange you should be fine.

 

[dw1305]

Hi all,

Should I run the airstone at night? I am just as concerned that running an airstone at night will create ph swings by driving off the co2 at night and then boosting co2 in the morning by turning airstone off? Co2 is running 24/7 of course. Am I worrying about nothing?

You can ignore pH, the changes in pH are due to the change in the CO2~carbonate equilibrium, but you do need to run an air-stone over-night.

You can't use the chart to estimate CO2 levels unless you know the dKH of the tank water, test kits measure alkalinity and it isn't the same thing for this purpose (although for most other functions it is). To get around this people use a drop checker (which has an air gap) contianing 4dKH solution and a narrow range pH indicator (bromothymol blue). This estimates CO2 levels quite well, but with the proviso that it takes some time for the drop checker to reflect the pH of the water, so you aren't monitoring CO2 levels in real time.

Personally I get around the risk of CO2 poisoning by not adding CO2.

cheers Darrel

 

[davidjp1982]

Hi all,
You can ignore pH, the changes in pH are due to the change in the CO2~carbonate equilibrium, but you do need to run an air-stone over-night.

You can't use the chart to estimate CO2 levels unless you know the dKH of the tank water, test kits measure alkalinity and it isn't the same thing for this purpose (although for most other functions it is). To get around this people use a drop checker (which has an air gap) contianing 4dKH solution and a narrow range pH indicator (bromothymol blue). This estimates CO2 levels quite well, but with the proviso that it takes some time for the drop checker to reflect the pH of the water, so you aren't monitoring CO2 levels in real time.

Personally I get around the risk of CO2 poisoning by not adding CO2.

cheers Darrel

I've got the api kh and gh liquid tests are these not accurate? It gives me a kh of 5 and gh 10. ph is at 6.6 at the moment I raised the internal filter up to ripple the surface as I figured even tanks with proper co2 and external filters will disturb the surface and now I'm not running an airstone and tank is overstocked I'd rather get some oxygen in at the cost of maybe losing some co2.

 

[davidjp1982]

Some pics as promised:

[/img]http://s30.postimg.org/x4d5fgjz3/09032014031.jpg[/img]

 

[davidjp1982]

 

[dw1305]

Hi all,

I've got the api kh and gh liquid tests are these not accurate?

It really depends upon a lot of factors, one problem is the for the dGH test the reagents need to be fairly new, as they aren't stable long term. In this case I'll mainly ignore dGH, (which is a measure of the multivalent cations (Ca++ etc.), mainly because it isn't really of any particular importance when you add CO2.

The dKH test measures alkalinity, rather than dKH, the tests uses titre-metric methodology where sulphuric acid (H2SO4) is added "drop by drop" until it neutralizes all the bases (hydroxides, (bi)carbonates, phosphates, etc.) in the water sample, and the colour changes. The colour change is just the pH indicator(s). Have a look at these for a bit more explanation: <http://www.skepticalaquarist.com/alkalinity> & <http://www.advancedaquarist.com/2002/2/chemistry>.

The bit of alkalinity we are interested is just the CO2 ~ carbonate equilibrium. When you add CO2 you change the pH, but you don't change the alkalinity.

The Bouncy Castle analogy
If that doesn't make sense and I don't know if this helps, but I'll use the "Bouncy Castle" analogy where "compressed air" substitutes for "added CO2". (This is from a thread at UKAPS <http://www.ukaps.org/forum/threads/ph-drop-high-alkalinity.30384/>)

When we aren't actively pumping air into the bouncy castle via a compressor, it is deflated and the air pressure inside and outside are the same, this is analogous to a fish tank where we aren't adding CO2.

When we turn the compressor on air is pumped into the castle and it inflates, in the case of CO2, when we add CO2 the HCO3- ~ H2CO3 equilibrium is driven towards H2CO3, you now have an extra H+ ion, and acids are defined as H+ donors, so the pH falls (the water becomes more acid).

If our bouncy castle doesn't have any holes in it, we don't need to add much compressed air to keep it inflated, or in the CO2 case this is the low dKH scenario where a small amount of CO2 addition causes a large pH drop. If the castle has a lot of holes we need to add a lot air to keep it inflated, and in the CO2 case this is the high dKH scenario.

But, rather than estimating how many holes we have, we can have a hole of standard size that always lets out the same amount of air, for CO2 this is the "4dKH solution in the drop checker scenario", where we add a stable amount of air ("CO2") to keep the castle inflated ("CO2 at 25ppm").

In all these cases if we turn the compressed air (CO2) off, the castle deflates and the HCO3- ~ H2CO3 equilibrium returns to its atmospheric level.

Personally for me the air compressor is always going to be turned off, as I can find quite enough ways to accidentally kill my fish without deliberately adding another one.

cheers Darrel