Oxyfern
Oxyfern is a non reproducing plant that converts 
Carbon Dioxide into breathable 
Oxygen (the rate seems related to the air pressure).
Ratios
The Oxyferns have quite similar gas conversion rates to the Duplicants, however they are about 3.2 times slower, and produce slightly more Oxygen than duplicants consume, which makes it impossible to cleanly match their number to the number of duplicants, leading to either Oxygen or Carbon Dioxide runaway overproduction.
| Oxygen (g/cycle) |
Carbon Dioxide (g/cycle) | |
|---|---|---|
| Duplicant | -60,000 | +1200 |
| Domesticated Oxyfern | +18,780 | -375 |
| Wild Oxyfern | +4,680 | -93.78 |
| Ratios (plants per duplicant) |
~3.19 | 3.2 |
| Ratios (wild) | ~12.8 | ~12.8 |
Domesticated Oxyferns convert about 98% of Water to Oxygen, which is still 10% more water-efficient than Electrolyzer (88% Water to Oxygen), with the additional cost of 4 kg per cycle Dirt.
As with any other plant, wild Oxyferns produce four times slower compared to domesticated ones, however they do not require Water or Dirt.
Growth
Oxyfern requires temperature range of 0 °C to 40 °C. It requires air pressure of 25 g to 10 kg, and Carbon Dioxide atmosphere. The plant has no growth cycle.
Domestic Oxyfern can be planted in a Planter Box, Farm Tile and Hydroponic Farm. It requires 4 kg per cycle Dirt and irrigation of 19 kg per cycle Water.
Heat economy
Since they produce 50 grams of oxygen at their body temperature for every gram of carbon dioxide consumed, and oxygen has 20% more specific heat than carbon dioxide, they have some heat deletion potential if the plants can be kept cool enough to grow in an atmosphere of very hot carbon dioxide. This is made easier by carbon dioxide's poor heat potential.
A single domestic oxyfern kept at 1 °C and slowly fed 500 °C carbon dioxide (similar to that from a carbon dioxide vent) will delete 0.625 g/s and 100 DTU/s in carbon dioxide relative to a target base temperature of 20 °C, and produce 31.3 g/s cold oxygen with a cooling potential of 600 DTU/s, for a total heat deletion of approximately 700 DTU/s, about half that of a wild wheezewort growing in oxygen, or a twentieth of a domestic wheezewort grown in hydrogen.
In general, the plants heat and cool very slowly while growing because they convert a small amount of the atmosphere they're in to a much larger amount of atmosphere at their own body temperature, cooling the area if it's warmer than them and warming it if it's cooler.
A single non-geotuned carbon dioxide vent produces about 105 g/s on average of carbon dioxide at 500 °C, enough to feed 170 domestic oxyferns, which can completely delete the carbon dioxide and replace it with 5.2 kg/s of oxygen, providing oxygen for 26 dupes and providing 100 kDTU/s of heat deletion relative to a 20 °C base if the ferns are kept at 1C. Obtaining this many seeds is impractical however, since they only spawn on map creation or are offered as a rare care package.
Pressure management
Oxyferns have a very high upper pressure limit for growth, and multiply the pressure of their input gas by 50, producing 50 grams of oxygen for every gram of carbon dioxide consumed.
Left unsealed, unchecked oxygen or carbon dioxide production might eventually overpressure your base. Since they will operate at a higher pressure range than the electrolyzer, oxygen diffuser, and standard gas vents, oxygen production from these will automatically stop if the oxyferns raise oxygen pressure in their areas too high. With good gas diffusion in your base and oxyfern farms, this means that overpressure from oxyferns alone will not happen as long as your oxyferns alone produce less oxygen than you're consuming. This does however have the unfortunate side effect of shutting down hydrogen gas production from any electrolyzers which will slow down or stop due to increased ambient oxygen, which can impact power generation.
If kept in a sealed box, it is extra important to remember that they multiply the mass of gas inputs by 50, so oxyferns initially grown at the bottom of a sealed box of 2 kg per tile carbon dioxide will eventually convert the room into 80% oxygen and 20% carbon dioxide at 10 kg per tile, at which point the ferns will stop growing due to overpressure. The highest carbon dioxide pressure at which they will never overpressure in a sealed room is 200 g carbon dioxide per tile, which they will convert to 10 kg per tile oxygen. This setup has the advantage of not requiring the player to worry about oxyferns overpressurizing the base, but requires pumping carbon dioxide in and oxygen out.
Tips
- Oxyfern Seed is sometimes offered as a Care Package. There is no other way to increase amount of Oxyferns on the map without seed splitting exploits.