Bottles suitable for DIY
- 1 or 2 liter PET bottles, e.g. B. for water, Cola, Fanta, Pepsi, etc. A hole is drilled into the lid with a drill or a red-hot nail. The CO2 hose is pushed through and sealed.
- Plastic bottles from Merck with a blue cap. These bottles can be ordered from pharmacies in different sizes, e.g. B. 500, 1000, 2500 and 5000cc.
- Various manufacturers offer ready-made sets for yeast fermentation. Bio-CO2 is usually spoken of. The sets contain all the necessary parts and can be refilled with your own mixtures. If a second original bottle is purchased, the next batch can be started while the previous batch is slowly coming to an end.
- 5 liter canisters are suitable for larger aquariums.
What a washing bottle is necessary
A washing bottle is used during yeast fermentation to prevent fermentation sludge, foam, yeast, sulphur, alcohol and other substances from the CO2 bottle from getting into the aquarium water.
The hose from the fermentation bottle should reach through the cap of the wash bottle to just above the bottom of the wash bottle. The end of the hose in the bottle is cut at an angle so that the bubbles don’t get into the water with an annoying blobb noise.
A second hose only extends about 1 centimeter into the wash bottle and goes through the lid into the aquarium.
The wash bottle is filled with water so that the second hose is not in the water. The CO2 and the impurities come into the wash bottle via the first hose.
The water in the wash bottle cleans the CO2. Because CO2 is a gas, it rises through the water. The impurities remain in the water. CO2 is heavier than air and therefore settles on the water surface of the wash bottle. The air is pushed out of the wash bottle.
The more CO2 is generated in the fermentation bottle, the more air escapes from the wash bottle through the hose into the aquarium. Eventually all the air will be out and CO2 will flow into the aquarium.
Because CO2 is not produced evenly, excess CO2 can be vented using a branch in the hose between the wash bottle and the aquarium.
There is an anoxic environment in the wash bottle. Traces of organic material, e.g. B. Alcohol vapors from the CO2 bottle can collect in the water of the wash bottle. There they are decomposed by sulfate-reducing bacteria. Traces of sulphate may be present in tap water. That’s enough to create a strong odor. Even the smallest amounts of hydrogen sulfide H2S smell strongly of rotten eggs. In aquarium water, H2S can kill the fish.
The water in the wash bottle must therefore be replaced regularly.
Some aquarists add common salt and a thin layer of sunflower oil to the water in the wash bottle. The salt is intended to kill any life forms that may be present and the oil to deflate any spilling yeast foam.
Why a check valve is necessary
At the beginning or end of the yeast fermentation, a negative pressure can arise in the CO2 bottle. This allows water to be sucked out of the aquarium.
A non-return valve should therefore always be used. The cheapest non-return valves from the aquarium trade are sufficient.
Can a CO2 bottle burst with yeast fermentation?
If the CO2 hose is simply hung in the aquarium, no pressure builds up in the CO2 bottle because the CO2 enters the aquarium water without any significant resistance.
Located at the end of the hose z. B. an air stone made of ceramic, the CO2 must first overcome the resistance of the air vent. For this purpose, a relatively high pressure builds up in the bottle until the CO2 is finally pushed through the vent.
The pressure only builds up when the bottle is started, until the first bubbles bubble out. From then on, the pressure in the bottle and in the hose remains the same. Small fluctuations due to the external air pressure etc. can be neglected.
The level of pressure does not depend on the amount of yeast, the temperature, etc., but only on the water depth of the outflow opening and the resistance of the outflow. If a check valve is installed in the hose, the resistance of the check valve is added.
If the bottle can withstand the first bubbles, nothing can happen later. The only danger is that the mixture will ferment so much that yeast will get through the hose into the vent and clog it. A wash bottle between the CO2 bottle and the aquarium can prevent this.
The frequently used PET bottles can withstand some pressure, so the risk of bursting is low.
Due to their size and properties, 5 liter beer kegs are very suitable for yeast fermentation. The enclosed rubber stoppers serve as a pressure relief valve. A beer keg can withstand over 2.5 bar of pressure.
For safety, a pressure protection can be installed in the respective system.
How the CO2 supply can be interrupted at night during yeast fermentation
Because fermentation cannot be interrupted, CO2 is introduced into the aquarium day and night during yeast fermentation. If the CO2 supply is not too high, the CO2 content and the pH value in the aquarium water are harmless to the fish.
If the fermentation is particularly strong, e.g. B. because too much yeast was used, CO2 values that are too high or strong fluctuations in the pH value can occur, especially at night when the plants do not consume CO2, so that fish could be harmed.
In small aquariums it is often difficult to adjust the fermentation so that not too much CO2 is added.
In such cases, interrupting the CO2 supply at night can make sense. In really critical cases, however, the CO2 supply should be switched off completely.
If a correctly dimensioned Paffrath bowl is used to introduce CO2, CO2 concentrations that are too high can hardly occur even with a constant CO2 supply.
Ways to switch off the CO2 supply:
- Open the fermenter lid, loosen, unscrew, etc.
- Remove the CO2 supply hose from the aquarium.
- Aerate the aquarium at night using a timer, ie supply oxygen with an air stone. CO2 is then expelled at night. How strong the effect is must be checked with a CO2 test.
- Insert a T-piece in the hose for the CO2 supply. A branch leads CO2 into the aquarium. A short piece of hose is attached to the other junction. The hose is opened or closed with a plug. A PVC pipe that fits snugly into the hose can be used as a plug. Inside the tube is sealed with hot glue. When using a hose clamp, the hose must be kinked and then “double clamped”. Shut-off valves do not close tightly enough because CO2 creeps through the smallest cracks.
Alternatively, the drain hose is opened or closed with a solenoid valve. There are also solenoid valves that can switch one input to two outputs. The solenoid valve is controlled with a timer.
The end of the drain line must be above the water surface to prevent water from draining from the aquarium. When the drain hose is opened, the CO2 flows into the room air because this path is easier for the gas than overcoming the water pressure from the aquarium. - Set the fermenter cooler at night and warmer during the day because the CO2 production depends on the temperature.
The CO2 supply must not simply be closed, e.g. B. with a hose clamp. As the fermentation continues, the pressure in the fermenter and in the hose continues to increase. In extreme cases, the bottle bursts, the hose jumps off, etc.
Control yeast fermentation with gelatin
Gelatine is used in yeast fermentation so that the fermentation runs as evenly as possible. This means that the strength and duration of fermentation can also be influenced within limits.
The resulting gel binds the sugar that the yeast needs as food to generate CO2. The CO2 systems from various manufacturers, often referred to as bio-CO2, also work according to this method.
With a suitable concentration of sugar, the amount of yeast added determines the strength of the CO2 production, ie how much CO2 is produced in a given period of time. The amount of sugar determines the duration of the CO2 production as long as the alcohol content does not become too high. The gelatine gradually makes new sugar available as food for the yeast.
Finished gel can only be stored in the refrigerator for a short time without water and yeast on top. Fungal or bacterial colonies form quickly, usually after 3 to 4 days.
Basic procedure:
- Sugar is dissolved in water.
- The sugar water is thickened with gelatine and filled into the fermentation tank.
- The fermentation tank is filled with water and some sugar as starter food.
- Fresh yeast or dry yeast is added to the water.
- The fermenter is shaken well to evenly distribute the yeast.
- After about 24 hours, fermentation begins.
- The fermentation lasts about 4 weeks.
When fermentation begins, how strong it is, and when it stops depends on how much sugar, water, and yeast is used. The yeast is not added to the gel. The yeast dies from the heat of the boil.
Suitable thickeners:
- gelatin
- Cake glaze or cake jelly
- Agar Agar
- agarose
- xanthan
Gelatin is a protein and is made by boiling bones. It consists of 86% water and 2% minerals.
Cake glaze or cake jelly is made from locust bean gum and is readily available in convenient quantities in supermarkets everywhere. 1 packet is enough for 1/2 liter of gel.
Agar Agar is a carbohydrate and is derived from seaweed. Agarose is even better than agar agar. Agar agar and agarose are available in various grades from major chemical companies such as Merck and Sigma.
Xanthan is available in shops that carry products from hobby shops, e.g. B. at spinning wheel.
recipes
Mixture with Agar Agar for 5 liter canister:
- Dissolve 300 grams of sugar in 1/4 liter of water.
- Add 6 grams of agar agar to the sugar water, bring to the boil briefly and then allow to cool slightly.
- Pour the mixture into a 5 liter canister.
- When the gel has cooled and set, add 1/2 teaspoon of baker’s yeast to the canister.
- Fill the canister with 4 liters of lukewarm water.
- After about 24 hours, connect the canister.
- At 20°C, fermentation is relatively even.
- About 40 bubbles per minute are generated.
- The fermentation time is around 2 weeks.
Mixture with cake jelly for 1.5 liter bottle:
- Dissolve 200 grams of sugar in 1/2 liter of water.
- Put 1 packet of cake jelly in the sugar water, bring to the boil briefly and then allow to cool slightly.
- Pour the mixture into a 1.5 liter bottle.
- When the gel has become cold and solid, fill the bottle with 1/2 liter of water.
- The gel is very thin. The gel therefore largely dissolves during fermentation so that the sugar is almost completely fermented. CO2 is produced longer.
Mixture with agarose
- The…