The first time I played Oxygen Not Included and looked at the different methods of generating oxygen, it didn’t take me long to realize that the Algae Terrarium seems to be more efficient than the Algae deoxydizer. But is it really?

More often than not we seem to look at efficiency as one resource being converted to another. I was just as guilty of this when playing Oxygen Not Included the first few times. Considering water an abundant resource was a huge mistake.

Short Answer

We recommend that you avoid the algae terrarium. It uses way too much water and produces polluted water which is a pain to handle in the early game.

Feel free to keep reading if you want to know more.

Oxygen Diffuser vs Algae Terrarium
Oxygen Diffuser vs Algae Terrarium – A friendly neighbour can be seen roaming around as well.

Long Answer

This isn’t going to be that complicated, just a bit of quick math to take a look at algae efficiency.

  1. Algae Terrarium uses 30 g/s of Algae to produce 40 g/s of Oxygen.
  2. Oxygen Diffuser uses 550 g/s of Algae to produce 500 g/s of Oxygen.

It looks quite clear-cut right? Is there no reason to use the Oxygen diffuser because the terrarium is a lot more efficient? Nope.

We all fell for it in our first few runs and some of us didn’t even bother to think about the consequences until we had dozens of abandoned colonies. The reason Oxygen Diffusers work a lot better is simple: They don’t need water.

Secondary Requirements

Let’s do a list, lists are nice.

  1. Algae Terrarium requires water.
  2. Oxygen Diffuser requires power.

Both of these require your dupes to work.

  1. Terrarium requires your dupes to bring bottled water to it. It also requires them to empty polluted water.
  2. Oxygen Diffuser on the other hand requires your dupes to work on the generator and produce power.

Later on in the game, power can be produced in a semi-automated manner reducing the workload on your dupes. Water on the other hand requires a lot of work. While playing Oxygen Not Included, you need to worry about more than just oxygen. The deoxydizer in our eyes is infinitely more efficient than the terrarium purely because it doesn’t require any water whatsoever.

Oxygen itself is barely a problem in this game, water is. Not being able to manage polluted water properly is the simplest of mistakes that are made by new players. A base that fully relies on oxygen production by terrariums will quickly convert all of its clean water to polluted water. You WILL run into water problems sooner or later, the terrarium just accelerates the process significantly.

For each Algae Terrarium in your base, you’re going through 300 grams of water every second, that’s 18 kg per minute. You need around eight terrariums to support your initial three dupes completely, that’s 144 kg of water every minute that’s being used to produce oxygen and not food.

Algae Problems

We’ve all been there, we’ve all had issues where out base runs out of algae and everything fails. It’s just a matter of fact that the starting zones have a limited amount of Algae and it’s very rare to come by on the rest of the map. You can convert slime to algae but eventually you’re going to run out of slime as well.

Now what?

We recommend moving your oxygen production away from resources which can be depleted. There’s a complete guide on different oxygen production methods in ONI, feel free to read through it.


  • Was there an update that changed something we talked about?
  • Did we forget to talk about something?
  • Are we wrong about something?

Let us know in the comments!