How to Find the Best Fuel for Bioreactor in Subnautica

Daniel Westrop
Daniel Westrop - Editor-In-Chief
7 Min Read

Are you looking for information about the best fuel for bioreactors in Subnautica? If you’re reading this, then you’ve probably played the game for quite a while and know that a fully powered base is essential to your survival. Without power, you won’t be able to charge your batteries or replenish your oxygen supply when entering your underwater habitat. These things are crucial in the early part of the game.

While the bioreactor isn’t the best power source in Subnautica (that title belongs to the nuclear reactor), it’s much more reliable compared to solar panels, which obviously only works during the day. A bioreactor will let you build a habitat farther from the surface, and its fragments are easily obtainable. That said, you’ll struggle to keep your base powered up if you don’t use the right power source.

In this article, we’ll show you everything you need to know about the bioreactor in Subnautica and the best power sources to use with it. Let’s get started!

Location of bioreactor fragments in Subnautica

Before anything else, we’ll go over how to build a bioreactor for your habitat in Subnautica. If you already have one, you can skip this section and go to bioreactor power sources.

To build the bioreactor, you’ll need to scan fragments (2) to obtain a blueprint for it. The good news is that they’re relatively easy to find. One good location to look for bioreactor fragments in Subnautica is an area called the “Grassy Plateau,” which is located a few hundred meters West of your lifepod. It’s a sandy biome characterized by large stone pillars and red blades of grass covering most of the seafloor. Just watch out for Sand Sharks!


Once you’ve collected the fragments, you’ll need the following materials:

  • 3x Titanium Ores
  • Wiring Kit
  • Lubricant

Once you’ve collected the materials, you can build the bioreactor inside your habitat using a habitat builder. If you’re wondering how to place a bioreactor in Subnautica, it’s important to note that it can only be built inside a multipurpose room (right in the middle).


Best Bioreactor power sources

At this point, you should now have a bioreactor powering your habitat. As the name implies, it converts organic matter into usable energy for your base of operations. However, how much power it generates depends on what organic matter you put inside it as fuel. It can be frustrating to return to your habitat to resupply, only to find that everything is powered down because your bioreactor in Subnautica is not working.

Simply put, what you put inside the bioreactor matters. As it turns out, the best fuel sources for a bioreactor in Subnautica are all fishes. The best one is called the Oculus.

An Oculus fish in an aquarium
An Oculus fish in an aquarium

As you can see above, the Oculus looks a lot like the common Peeper fish, only bigger and with large bioluminescent eyes. If placed inside a bioreactor, it produces 10,080 units of power per load (per fish); the highest in the game. That said, these fishes can be difficult to obtain since they’re only found in the Jellyshroom cave — a cave biome crawling with large predatory snake-like creatures called the Crabsnake. These creatures are highly aggressive and will attack you on sight.

The Jellyshroom Caves
The Jellyshroom Caves

Another problem is the total depth of the biome (up to 300 meters) which rapidly depletes your oxygen levels if you’re not equipped with a rebreather. Even then, you only have a few seconds to explore the biome, and you’ll have to return to the surface to replenish your oxygen supply. For these reasons, it is recommended that you explore the biome with an upgraded Seamoth (at least MK1 depth module) and a high-capacity oxygen tank. A first aid kit, food, and water wouldn’t hurt either.

If you don’t have access to the multipurpose room yet, then you’d be interested to know that the Jellyshroom cave is also one of the few places in the game where you can get blueprints for it. Just look for an abandoned habitat/structure located somewhere in the cave. 

Once you’ve progressed far enough into the game, you’ll be able to build an alien containment unit. It’s basically a large aquarium that you can build inside the habitat, and you can use it to breed Oculus fishes in the safety of your base. 

Alternative fuel sources for your bioreactor

Are you having trouble sourcing Oculus fishes for your bioreactor? Well, exploring the Jellyshroom cave can be difficult, especially in the early parts of the game. An easier alternative would be to use either a Reginald or a Spadefish. Both are abundant and relatively easy to find (there are plenty of them in the Grassy Plateaus).

In case you’re wondering, this is what these fishes look like:

A Reginald fish in an aquarium
A Reginald fish in an aquarium

A Spadefish in an aquarium
A Spadefish in an aquarium

If placed inside the bioreactor, the Reginald fish produces 7840 units of power per load. The Spadefish produces 6720 units of power per load. This makes them the second and third best fuel sources that you can use on your bioreactor. Plus, there’s no danger going after these fishes at all since they’re pretty common and thrive pretty close to the surface.


So there you have it — everything that you need to know about the Bioreactor in Subnautica and the best fuel sources for it. You might feel differently about putting a fish inside a bioreactor, but it isn’t any worse than cooking them in a fabricator. 

Subnautica is a survival adventure game after all, and you have to make good use of any resource you can find. If anything else, using the right fuel for your bioreactor will help you progress into the game a lot more smoothly.

Need help with another game? You might want to check out our Game Guides for more information.

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By Daniel Westrop Editor-In-Chief
Hey, folks! I'm Daniel Westrop, your friendly Editor-in-Chief at WhatIfGaming. Started my gaming saga in '03 with Unreal Tournament and never hit pause. I'm all about that PC life, though I cheat with my Xbox (only for Forza, I promise!). From being a Global Elite in CS2 to a Fortnite veteran, I've got tales. Minecraft architect? Check. MW2 strategist? Absolutely. My real-life "squad" is a league of extraordinary writers worldwide, making gaming lore legend.

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