Subnautica Gel Sack — Where to Find It and How to Farm Aerogel

The Gel Sack is a squishy, edible, bioluminescent plant that exists for exactly one reason in most playthroughs: it's the core ingredient of Aerogel (1 Gel Sack + 1 Ruby), the advanced material you need to build the Prawn Suit and its best modules. It grows on cave walls in the deep biomes — Grand Reef, Blood Kelp, the Lost River, the Dunes and a handful of others — and it's one of the few plants you can genuinely farm, since knife-harvested spores plant into an Exterior Growbed. This guide covers every spawn location, the harvest math, and the aerogel recipes that matter.

Here's what you'll learn:

• Every biome where gel sacks spawn, ranked by convenience
• The exact spore-harvesting rules (3 spores per sack, then it's gone)
• How the growbed loop makes gel sacks infinite
• Every aerogel recipe and how many you need total

Official resources: Steam store page · Official Subnautica Wiki — Gel Sack · Official Subnautica Wiki — Aerogel · IGN Subnautica page · Wikipedia — Subnautica

Per the official Subnautica Wiki: "While the gel sack is edible, its low-density renders it an invaluable advanced construction material." The wiki's scanner entry calls it "edible — aerogel construction applications" in one line.

Where to Find Gel Sacks

Gel sacks attach to walls and slopes in deep biomes. The wiki's full biome list, ranked by how convenient they are to reach:

What Is a Gel Sack Used For?

Aerogel. The official recipe: 1 Gel Sack + 1 Ruby = 1 Aerogel at the Fabricator. Ruby is found in shale outcrops and loose on the seafloor in the deep biomes — the wiki lists the Grand Reef, Blood Kelp, Lost River and Lava Zones as the main ruby sources.

Aerogel, in turn, feeds high-end construction:

The Prawn Suit — 2 Aerogel plus 2 Plasteel Ingots, 1 Enameled Glass, 2 Diamonds and 2 Lead — is the main sink, which is exactly why the Prawn Suit guide and the gel sack farming loop tend to be planned together.

Harvesting and Farming

Two ways to harvest, and the rules are precise (from the wiki):

• Pick it up whole — the sack goes in your inventory intact, ready for aerogel (or eating).
• Knife it for spores — one Gel Sack Spore per knife strike, up to 3 spores, and the third strike destroys the sack. Spores plant into an Exterior Growbed (and an Interior Growbed with the right upgrades).

The farming loop: knife a few sacks for spores → plant the spores in growbeds → the grown sacks are pickable for aerogel, and you can keep knifing some of them for more spores. Once the growbeds are running, you never need to dive for gel sacks again.

How Many Gel Sacks Do You Need?

Plan for 6–10 sacks before building the Prawn Suit:

• 2 sacks → 2 Aerogel for the Prawn Suit itself
• 1–2 spare sacks for aerogel-dependent module crafting
• A few extra as backup rations

Because the spawns are spread across deep, dangerous biomes, the efficient play is: grab the Northwestern Mushroom Forest sack early, then do one Grand Reef/Blood Kelp sweep for 6–8 sacks, and plant spores into a growbed at your main base the moment you have the blueprint. The Bioreactor angle is a bonus: gel sacks burn for 245 energy each, and gel sack spores for 7, so the growbed doubles as emergency power.

FAQ

Where do I find gel sacks in Subnautica?

Grand Reef, Deep Grand Reef, Blood Kelp Zone, Lost River, Dunes, Mountains slopes, the Northwestern Mushroom Forest (base of the giant tree), Sea Treader's Tunnel Caves and a few smaller caves. The Grand Reef is the biggest single source.

What is a gel sack used for?

It's the core ingredient of Aerogel (1 sack + 1 Ruby). Aerogel builds the Prawn Suit and its high-end modules. It's also edible (+5 food, +4 water) and a strong Bioreactor fuel (245 energy per sack).

How do I get aerogel in Subnautica?

Craft it at the Fabricator from 1 Gel Sack + 1 Ruby. Ruby comes from shale outcrops and the deep-biome seafloor — Grand Reef, Blood Kelp and the Lost River are the reliable spots.

Can I grow gel sacks?

Yes. Knife a sack to harvest up to 3 spores, then plant the spores in an Exterior Growbed. Grown sacks are pickable for aerogel, and the loop makes the material renewable.

How many gel sacks do I need for the Prawn Suit?

2 gel sacks (2 aerogel) for the Prawn Suit itself, plus 1–2 spares for aerogel-dependent modules — aim for 6–10 total in one deep sweep so you never have to go back.

Related Guides

• Subnautica Prawn Suit Guide — Fragments, Arms and Upgrades
• Subnautica Mushroom Forest — Location, Resources and Wrecks
• Subnautica Kyanite Guide — Lava Zones and Endgame Recipes
• Subnautica Multipurpose Room Guide — Blueprint, Building and Power
• Subnautica Below Zero Map — Biomes, Coordinates & Navigation

Last updated: August 13, 2026.