Subnautica Bioreactor — Recipe, Fuel Values and Best Uses

The Bioreactor is Subnautica's organic power generator: a base module that burns fish, eggs and plant matter for energy at a steady 50 energy per minute, with 500 energy of internal storage — enough to run a small outpost's chargers indefinitely. It needs only 2 fragments to unlock (grassy plateaus wrecks, kelp forest and sparse reef), costs 3 Titanium + 1 Wiring Kit + 1 Lubricant to build, and sits in the center of a Multipurpose Room or Large Room. Its whole game is fuel choice: an Oculus gives 630 energy per slot (the best ratio in the game), a Reginald gives 490, and a stack of Marblemelons or Lantern Fruit keeps a farm base topped up for free. This guide covers the recipe, every fuel value that matters, and how it compares to solar, thermal and nuclear.

Here's what you'll learn:

• Where the fragments spawn and the exact build recipe
• How the machine works (and its one annoying limitation)
• The full fuel value table — what to burn and what to sell
• How to set up infinite fuel with Alien Containment breeding
• Bioreactor vs Solar vs Thermal vs Nuclear, with numbers

Official resources: Steam store page · Official Subnautica Wiki — Bioreactor · Official Subnautica Wiki — Alien Containment · IGN Subnautica page

What Is the Bioreactor and How Do You Unlock It?

The Bioreactor is an interior base piece built with the Habitat Builder that "composts organic matter into electrical energy." Mechanically it has a 4×4 inventory grid (16 slots) for fuel, produces 1 unit of energy every 1.2 seconds (50 per minute), and stores up to 500 energy. It can only be placed in the center of a Multipurpose Room or a Large Room, and it has no effect in Creative mode. The one rule that catches everyone: items placed inside cannot be removed — what you feed it is burned for good.

To unlock it, scan 2 Bioreactor Fragments. Per the official wiki they spawn on the seabed, in Grassy Plateaus wrecks, in the Kelp Forest and in the Sparse Reef — all shallow, all reachable in the first few hours. The build recipe at the Fabricator:

Per the official Subnautica Wiki — Bioreactor: "The Bioreactor produces 1 unit of energy every 1.2 seconds (50 per minute), with a maximum capacity of 500 units per Bioreactor. It can only be placed in the centers of a Multipurpose Room or Large Room."

Bioreactor Fuel Values (The Full Table)

Energy output depends entirely on what you feed it. These are the official values for the fuels that actually matter:

Two rules of thumb from the numbers: egg-hatched fish give the most energy (the official wiki notes this explicitly), and the Oculus has the best energy-to-slot ratio in the game — 630 energy for a single 1×1 slot, a fact confirmed by the wiki and echoed across Reddit and Steam community threads.

Best Fuel Strategies (What to Actually Burn)

• Early game (Safe Shallows / Kelp Forest): Peeper, Garryfish, Spadefish and Eyeye all give 420 energy and swarm the starting biomes. One dive's worth of catch keeps a base running for hours. Marblemelons and Lantern Fruit from a growbed are the zero-effort plant option — a full 4-slot stack of Lantern Fruit burns for 840 energy total.
• Mid game: the Reginald is the community's favourite farmable fuel — 490 energy per fish, easy to catch in the Grassy Plateaus, and also the best food in the game (cooked/cured), so one species covers both needs. Our fish guide has the full species breakdown.
• Late game / permanent bases: the Oculus farm above, or Blood Oil / Marblemelon if you're going full plant. Alien Feces (300) is a decent waste-disposal bonus from your containment tank.

Bioreactor vs Solar, Thermal and Nuclear

Every generator in Subnautica has its own numbers, and the community consensus is "thermal is the endgame king, nuclear is the brute-force answer, bio is the flexible starter." From the official wiki's Energy page:

The Bioreactor's niche: it works anywhere, day or night, at any depth, with fuel you can farm from organic matter on site — ideal for Kelp Forest and Mushroom Forest bases where solar is weak, and for outposts running a Battery or Power Cell Charger. Its weakness is throughput: it can't sustain heavy consumers like multiple Water Filtration Machines. The Thermal Plant beats it once you have a heat source (see our Thermal Plant guide for the output math), and the Nuclear Reactor leaves it behind entirely for endgame bases — full comparison in our Nuclear Reactor guide. Practical split most players settle on: solar early, bioreactor for mid-game outposts, thermal or nuclear for the permanent base.

Fun facts from the official wiki's trivia section, so you know what you're dealing with: the Bioreactor originally sat outside the base like a Solar Panel (changed before release), it used to accept only Creepvine Samples and Fungal Samples, and the two things that famously can't go in are Spiked Horn Grass and Cuddlefish — so no, you can't power your base with cuddlefish, which is exactly the question Reddit keeps asking.

FAQ

What is the Bioreactor used for in Subnautica?

It's an interior base generator that converts fish, eggs and plant matter into power: 50 energy per minute with 500 storage. It runs anywhere at any depth, which makes it ideal for outposts and sunless biomes.

Where do I find Bioreactor fragments?

Scan 2 Bioreactor Fragments from the seabed, Grassy Plateaus wrecks, the Kelp Forest or the Sparse Reef. It unlocks early — all four spawn zones are shallow biomes.

What is the best Bioreactor fuel?

The Oculus: 630 energy for one inventory slot, the best ratio in the game, and infinitely farmable by breeding in Alien Containment. The Reginald (490) is the best easily-caught alternative, and Peeper/Garryfish/Spadefish (420 each) are the early-game workhorses.

Can I take items back out of a Bioreactor?

No. Anything placed in the 4×4 grid is consumed permanently. Double-check before you feed it your last cooked fish.

Is the Bioreactor or the Nuclear Reactor better?

Nuclear wins on raw output (250/min, 2,500 storage vs 50/min, 500) but needs reactor rods and uranium. The Bioreactor is cheaper, renewable and available much earlier. Most players use the Bioreactor mid-game and switch to thermal/nuclear for endgame bases.

Related Guides

• Subnautica Multipurpose Room — Blueprint, Uses & Build Tips
• Subnautica Alien Containment — How to Breed Fish for Food & Fuel
• Subnautica Nuclear Reactor — Recipe, Rods & Power Output
• Subnautica Thermal Plant — Recipe, Fragments & Placement
• Subnautica Power Cell Charger — Recipe & Where to Build
• Subnautica Fish — Every Species, Where to Find Them & Uses

Last updated: August 13, 2026.