http://www.practicalfishkeeping.co.uk/pfk/pages/show_article.php?article_id=606
CO2 systems for the planted aquarium don't have to be expensive or complex, as George Farmer explains...
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The vast majority of aquarium plants benefit from carbon dioxide (CO2) injection. Around 40% of the plants are made from carbon and the easiest way most plants extract carbon from the water (or air for emerged plants) is via the CO2 present.
Generally speaking, a lack of CO2 limits growth, providing there are sufficient lighting levels. However, even planted aquariums with lower lighting levels will benefit from CO2 injection.
Another advantage is that CO2 creates a more acidic environment and helps shift the balance between ammonia/ammonium in favour of the less toxic ammonium.
Many tropical freshwater fish, such as tetras, barbs, loaches, Corydoras sp., Angelfish, Discus, Rams, gouramis, plecs, and Betta sp., prefer the more acidic environment that CO2 injection produces.
A pressurised system is the preferred method for most situations as it is the most convenient, controllable and reliable technique for providing a stable CO2 supply to your aquarium.
However, these systems are relatively expensive, typically costing between £100 and £500, depending on the manufacturer and specifications.
Yeast-based systems
The most popular alternative to the pressurised system is fermentation. Sugar, yeast and water are mixed in a suitable container and a bio-chemical reaction results in the production of CO2 gas.
This gas is then delivered to the aquarium water via tubing and finally to a diffuser of some description that allows the CO2 to dissolve into the water.
The main advantage of a yeast-based system is its relatively low cost and simplicity, but there are disadvantages.
Providing a suitable and stable CO2 level in larger aquariums, ie. over 100 l./22 gal., may prove difficult, as the output from a yeast-based system is limited and fluctuates as the yeast, sugar and water react over time.
Stable CO2 output will generally last a maximum of 2-3 weeks, peaking in the first few days, then being fairly stable before tailing off. Before the CO2 output becomes too low, it's important to change the mixture as low or unstable CO2 is a very common algae trigger.
A very effective technique at providing suitable and stable levels for larger aquariums is to use multiple units. The mixtures can then be used in a staggered format, producing a relatively constant CO2 output.
Make your own
You can concoct your own yeast-based CO2 system using commonly available, cheap household products. This system should provide enough CO2 for a typical planted 100 l./22 gal. aquarium for 2-3 weeks.
Yeast reactor assembly
1. Drill a 6mm hole in the centre of the bottle cap.
2. Insert 6mm tubing so approx. 2.5cm/1†protrudes into the bottle.
3. Use silicone sealant to seal tubing on both sides of bottle cap.
4. Allow sealant to dry.
5. Test the seal is working by tightening the bottle cap and sucking on the end of the tubing; the bottle should collapse due to the vacuum created and should not expand until you relax your breath.
Note – it is very important to use a suitable bottle ie. a plastic bottle that has contained a carbonated drink. These are designed to withstand high pressures. DO NOT use a glass bottle.
Recipes and ratios
The ratio of water, sugar and yeast can be adjusted to suit individual requirements. Think of the sugar and water as the CO2 'fuel'.
Generally speaking the more sugar the longer the mixture will last. The vital ingredient is the yeast, so think of this as the CO2 'throttle'. The more yeast in the mixture, the faster the reaction and the more CO2 produced.
Remember, though, that the faster the CO2 production, the less time the mixture will last. The bicarbonate of soda apparently stabilises the CO2 production but many hobbyists have noted that it does little to affect output.
However in very soft water of less than GH 4, it can prevent sporadic output and frothing from the mixture.
There is no standard recipe suitable for all situations. Each planted aquarium will have its own CO2 requirement dependent on various factors like tank size, water agitation (more agitation or surface/air interface means more CO2 requirement), lighting, plant species, water chemistry and even ambient temperature.
The higher the ambient temperature, the faster the fermentation process. This is worth noting on hot summer days as the CO2 level may increase quite noticeably. Likewise on cold days, the CO2 output may decrease.
Some off-the-shelf kits actually come with insulating material wrapped around the mixture container. I have known some hobbyists to wrap thermal socks around their units!
Recipe and setting up
The following should provide a suitable CO2 output for most planted aquariums ranging in size from 25 l./5.5 gal. to 100 l./22 gal.
200g sugar
1/4 to1 teaspoon yeast
1/2 to 2 teaspoon bicarbonate of soda (if required)
800ml water
1. Fill the bottle with sugar using a funnel. Add the yeast and bicarb, then add the water. Ensure the water is tepid (30°C/86°F or so is ideal). Too cold and the mixture won't react, too hot and it will kill the yeast. Mixing is not necessary.
2. Attach bottle cap/tubing and tighten cap.
3. Place the tubing and diffuser in the aquarium. If you do not have a diffuser, positioning the tube's CO2 output near the filter intake is effective in most situations.
There should be visible bubbles in the aquarium after an hour or so. The empty void in the bottle will need to fill with CO2 before any bubbles present, so be patient!
CO2 output will peak after a few days then should be fairly constant for approx. 14 days. Change the mixture before the output reduces excessively, as low CO2 can lead to algae problems.
Test for CO2 regularly for the first few days to ensure levels are within limits and monitor fish behaviour.
Testing CO2 levels
Ideal CO2 levels are 25–35ppm, however any level over 15ppm should result in noticeably higher growth rates. Aquariums with higher lighting levels, ie. 3 or more T8 tubes, should aim for a stable 30ppm.
Testing is simple; you need a pH and KH test kit and the results are then cross-referred to a pH/KH/CO2 table. PFK has a CO2 calculator on its website – www.practicalfishkeeping.co.uk
CO2 levels over 35ppm can cause fish health issues, so beware. Excess CO2 can be easily driven-off by using an airstone or increasing surface agitation using the filter output.
Typical CO2 intoxication symptoms in fish include gasping at the surface and being drowsy, slow-to-react behaviour. Generally speaking, excessive CO2 levels are rare using yeast-based systems, unless the aquarium is particularly small.
In normal circumstances, avoid using airstones and minimise surface agitation to help keep up CO2 levels.
Changing the output
Keep the sugar and water quantities constant and CO2 output can then be modified to suit by changing the quantity of yeast. Remember less yeast = lower CO2 output, but for a longer time. More yeast = higher output, but for a shorter time.
Larger aquariums can use two or three units to good effect. Changing the mixtures alternately will help provide a stable CO2 output.
Obviously, there will be a large degree of trial and error when determining an ideal recipe for your aquarium but this article should provide a good starting point. As a rough guide, one bubble every 4 seconds is ideal for a 100 l./22 gal. planted aquarium.
Test the CO2 level regularly and adjust the bubble rate accordingly by increasing or decreasing the yeast until a 25–35ppm CO2 level is obtained. After some time you will establish a routine where you know exactly how much yeast to add and how often you need to change the mixture.
Commercial yeast-based/fermenting systems
If you'd like to buy an off-the-shelf unit, there are several available, priced from around £10 for models with a basic diffuser, up to £40 for more sophisticated kits. They include:
Dennerle Bio-Line CO2 series
Ferplast CO2 Energy Classic
Hydor CO2 Green NRG Natural System
Nutrafin Natural Plant System CO2
Red Sea Turbo Bio System
One product I've had good results with is the Nutrafin Natural Plant System. These are good value (around £15–£25 depending on retailer) and come with an effective diffuser. Each unit is designed for a 70 l./16 gal. aquarium.
I ran two units in my 125 l./27 gal. heavily planted tank and replaced the supplied sachets of 'Activator' and 'Stabiliser' with dried bread-making yeast and bicarbonate of soda, both available from the supermarket.
I used half a teaspoon of yeast and 1 teaspoon of bi-carbonate of soda in each unit, changing the mixtures alternately every 10 days or so to give me a stable CO2 level of around 25ppm.
Half a teaspoon of yeast is a higher quantity than supplied by the Nutrafin 'Activator' sachets. This is deliberate as using more yeast produces more CO2.
Safety First
1. Fit a check valve to the tubing to ensure the aquarium water does not back-syphon into the bottle.
2. Keep the bottle upright at all times and keep out of reach of children and pets.
3. It is vital that no yeast mixture enters the aquarium as it may cause health problems for the fish. If any mixture does enter, immediately remove the tubing and perform regular partial water changes until the water becomes clear. Monitor fish behaviour closely and add an airstone if available.
4. There is a very low risk of the bottle exploding caused by a blockage. If regular maintenance is carried out (ie. inspecting the tubing etc. regularly) there shouldn't be a problem.
Equipment
2 l. plastic fizzy drink bottle and cap
6mm tubing
Drill and 6mm bit
Silicone sealant
Granulated white sugar
Dried yeast
Bicarbonate of soda (not essential)
Weighing scales
Measuring jug
5ml teaspoon
One-way check valve
Diffuser (optional)
CO2 systems for the planted aquarium don't have to be expensive or complex, as George Farmer explains...
The vast majority of aquarium plants benefit from carbon dioxide (CO2) injection. Around 40% of the plants are made from carbon and the easiest way most plants extract carbon from the water (or air for emerged plants) is via the CO2 present.
Generally speaking, a lack of CO2 limits growth, providing there are sufficient lighting levels. However, even planted aquariums with lower lighting levels will benefit from CO2 injection.
Another advantage is that CO2 creates a more acidic environment and helps shift the balance between ammonia/ammonium in favour of the less toxic ammonium.
Many tropical freshwater fish, such as tetras, barbs, loaches, Corydoras sp., Angelfish, Discus, Rams, gouramis, plecs, and Betta sp., prefer the more acidic environment that CO2 injection produces.
A pressurised system is the preferred method for most situations as it is the most convenient, controllable and reliable technique for providing a stable CO2 supply to your aquarium.
However, these systems are relatively expensive, typically costing between £100 and £500, depending on the manufacturer and specifications.
Yeast-based systems
The most popular alternative to the pressurised system is fermentation. Sugar, yeast and water are mixed in a suitable container and a bio-chemical reaction results in the production of CO2 gas.
This gas is then delivered to the aquarium water via tubing and finally to a diffuser of some description that allows the CO2 to dissolve into the water.
The main advantage of a yeast-based system is its relatively low cost and simplicity, but there are disadvantages.
Providing a suitable and stable CO2 level in larger aquariums, ie. over 100 l./22 gal., may prove difficult, as the output from a yeast-based system is limited and fluctuates as the yeast, sugar and water react over time.
Stable CO2 output will generally last a maximum of 2-3 weeks, peaking in the first few days, then being fairly stable before tailing off. Before the CO2 output becomes too low, it's important to change the mixture as low or unstable CO2 is a very common algae trigger.
A very effective technique at providing suitable and stable levels for larger aquariums is to use multiple units. The mixtures can then be used in a staggered format, producing a relatively constant CO2 output.
Make your own
You can concoct your own yeast-based CO2 system using commonly available, cheap household products. This system should provide enough CO2 for a typical planted 100 l./22 gal. aquarium for 2-3 weeks.
Yeast reactor assembly
1. Drill a 6mm hole in the centre of the bottle cap.
2. Insert 6mm tubing so approx. 2.5cm/1†protrudes into the bottle.
3. Use silicone sealant to seal tubing on both sides of bottle cap.
4. Allow sealant to dry.
5. Test the seal is working by tightening the bottle cap and sucking on the end of the tubing; the bottle should collapse due to the vacuum created and should not expand until you relax your breath.
Note – it is very important to use a suitable bottle ie. a plastic bottle that has contained a carbonated drink. These are designed to withstand high pressures. DO NOT use a glass bottle.
Recipes and ratios
The ratio of water, sugar and yeast can be adjusted to suit individual requirements. Think of the sugar and water as the CO2 'fuel'.
Generally speaking the more sugar the longer the mixture will last. The vital ingredient is the yeast, so think of this as the CO2 'throttle'. The more yeast in the mixture, the faster the reaction and the more CO2 produced.
Remember, though, that the faster the CO2 production, the less time the mixture will last. The bicarbonate of soda apparently stabilises the CO2 production but many hobbyists have noted that it does little to affect output.
However in very soft water of less than GH 4, it can prevent sporadic output and frothing from the mixture.
There is no standard recipe suitable for all situations. Each planted aquarium will have its own CO2 requirement dependent on various factors like tank size, water agitation (more agitation or surface/air interface means more CO2 requirement), lighting, plant species, water chemistry and even ambient temperature.
The higher the ambient temperature, the faster the fermentation process. This is worth noting on hot summer days as the CO2 level may increase quite noticeably. Likewise on cold days, the CO2 output may decrease.
Some off-the-shelf kits actually come with insulating material wrapped around the mixture container. I have known some hobbyists to wrap thermal socks around their units!
Recipe and setting up
The following should provide a suitable CO2 output for most planted aquariums ranging in size from 25 l./5.5 gal. to 100 l./22 gal.
200g sugar
1/4 to1 teaspoon yeast
1/2 to 2 teaspoon bicarbonate of soda (if required)
800ml water
1. Fill the bottle with sugar using a funnel. Add the yeast and bicarb, then add the water. Ensure the water is tepid (30°C/86°F or so is ideal). Too cold and the mixture won't react, too hot and it will kill the yeast. Mixing is not necessary.
2. Attach bottle cap/tubing and tighten cap.
3. Place the tubing and diffuser in the aquarium. If you do not have a diffuser, positioning the tube's CO2 output near the filter intake is effective in most situations.
There should be visible bubbles in the aquarium after an hour or so. The empty void in the bottle will need to fill with CO2 before any bubbles present, so be patient!
CO2 output will peak after a few days then should be fairly constant for approx. 14 days. Change the mixture before the output reduces excessively, as low CO2 can lead to algae problems.
Test for CO2 regularly for the first few days to ensure levels are within limits and monitor fish behaviour.
Testing CO2 levels
Ideal CO2 levels are 25–35ppm, however any level over 15ppm should result in noticeably higher growth rates. Aquariums with higher lighting levels, ie. 3 or more T8 tubes, should aim for a stable 30ppm.
Testing is simple; you need a pH and KH test kit and the results are then cross-referred to a pH/KH/CO2 table. PFK has a CO2 calculator on its website – www.practicalfishkeeping.co.uk
CO2 levels over 35ppm can cause fish health issues, so beware. Excess CO2 can be easily driven-off by using an airstone or increasing surface agitation using the filter output.
Typical CO2 intoxication symptoms in fish include gasping at the surface and being drowsy, slow-to-react behaviour. Generally speaking, excessive CO2 levels are rare using yeast-based systems, unless the aquarium is particularly small.
In normal circumstances, avoid using airstones and minimise surface agitation to help keep up CO2 levels.
Changing the output
Keep the sugar and water quantities constant and CO2 output can then be modified to suit by changing the quantity of yeast. Remember less yeast = lower CO2 output, but for a longer time. More yeast = higher output, but for a shorter time.
Larger aquariums can use two or three units to good effect. Changing the mixtures alternately will help provide a stable CO2 output.
Obviously, there will be a large degree of trial and error when determining an ideal recipe for your aquarium but this article should provide a good starting point. As a rough guide, one bubble every 4 seconds is ideal for a 100 l./22 gal. planted aquarium.
Test the CO2 level regularly and adjust the bubble rate accordingly by increasing or decreasing the yeast until a 25–35ppm CO2 level is obtained. After some time you will establish a routine where you know exactly how much yeast to add and how often you need to change the mixture.
Commercial yeast-based/fermenting systems
If you'd like to buy an off-the-shelf unit, there are several available, priced from around £10 for models with a basic diffuser, up to £40 for more sophisticated kits. They include:
Dennerle Bio-Line CO2 series
Ferplast CO2 Energy Classic
Hydor CO2 Green NRG Natural System
Nutrafin Natural Plant System CO2
Red Sea Turbo Bio System
One product I've had good results with is the Nutrafin Natural Plant System. These are good value (around £15–£25 depending on retailer) and come with an effective diffuser. Each unit is designed for a 70 l./16 gal. aquarium.
I ran two units in my 125 l./27 gal. heavily planted tank and replaced the supplied sachets of 'Activator' and 'Stabiliser' with dried bread-making yeast and bicarbonate of soda, both available from the supermarket.
I used half a teaspoon of yeast and 1 teaspoon of bi-carbonate of soda in each unit, changing the mixtures alternately every 10 days or so to give me a stable CO2 level of around 25ppm.
Half a teaspoon of yeast is a higher quantity than supplied by the Nutrafin 'Activator' sachets. This is deliberate as using more yeast produces more CO2.
Safety First
1. Fit a check valve to the tubing to ensure the aquarium water does not back-syphon into the bottle.
2. Keep the bottle upright at all times and keep out of reach of children and pets.
3. It is vital that no yeast mixture enters the aquarium as it may cause health problems for the fish. If any mixture does enter, immediately remove the tubing and perform regular partial water changes until the water becomes clear. Monitor fish behaviour closely and add an airstone if available.
4. There is a very low risk of the bottle exploding caused by a blockage. If regular maintenance is carried out (ie. inspecting the tubing etc. regularly) there shouldn't be a problem.
Equipment
2 l. plastic fizzy drink bottle and cap
6mm tubing
Drill and 6mm bit
Silicone sealant
Granulated white sugar
Dried yeast
Bicarbonate of soda (not essential)
Weighing scales
Measuring jug
5ml teaspoon
One-way check valve
Diffuser (optional)