How do I unlock aquaculture in Probably Stolen?
Buy Water Trading in Joe Wild's network, then Aquaculture. It gives you a starter kit and a weekly visit from the Retired Aquafarmer.
Probably Stolen Aquaculture
In Probably Stolen, fish farming is called Aquaculture, and it came to the demo in the October 19, 2026 update. Buy Water Trading in Joe Wild's network first, then Aquaculture. You get an Aquaculture Starter Kit with a fish tank and fertilized tilapia roe, and a Retired Aquafarmer starts visiting once a week. The tank needs a water tank, power and filters. Tilapia eat fish feed and breed on their own; eels and sturgeon eat meat, don't breed, and pay you back in luxury fillets, battery charge and caviar.
How fish farming works in Probably Stolen
For what the game is and every guide we publish, start at the Probably Stolen guide hub.
- Unlock order: Water Trading, then Aquaculture, then Aquaculture II for bigger fish.
- The tank: a Recirculating Aquaculture System with its water tank, an Energy Cell and Water Filters.
- Food: Gutterflow Pellets and Industrial Fish Feed for tilapia; meat for eels and sturgeon.
- More fish: tilapia lay eggs; every other fish comes from the Retired Aquafarmer.
- What you get: fish fillets, eel fillets, caviar and a skin graft that works as a bandage.
Probably Stolen aquaculture at a glance
| Field | Value |
|---|---|
| How to unlock | Buy Aquaculture in Joe Wild's network. Source: In-game text. |
| Needed first | Water Trading; Aquaculture II needs Aquaculture. Source: The game's data; in-game prompt. |
| Starter kit | Fish tank and water tank, fertilized tilapia roe, an Energy Cell, a jug of Rustwater, two bags of fish feed, a Kitchen Knife and a Marking Pen. Source: The game's data. |
| Fish seller | The Retired Aquafarmer, once a week. Source: In-game text. |
| The tank | Needs a water tank, power and filters. Source: In-game text. |
| Feed | Gutterflow Pellets and Industrial Fish Feed, both for fish only. Source: In-game text. |
| Fish that breed | The three tilapia; eels and the Sturgeon do not breed in captivity. Source: In-game text; the game's data. |
| What you harvest | Fish and eel fillets, Caviar, Sturgeon Roe and Tilapia Skin Graft. Source: In-game text. |
How to unlock aquaculture
Fish farming is a favor in Joe Wild's network. Its entry reads: "Wild will refer you to a retired aquafarmer who will visit you once a week, selling fish farming equipment and fertilized roe. Immediately receive an Aquaculture Starter Kit. (Unlocks Aquaculture Content.)"
Buy Water Trading first. In the game's data, Aquaculture lists Water Trading as its prerequisite. Until you own Water Trading, the network shows "This upgrade requires Water Trading." instead of letting you buy it. Aquaculture II in turn requires Aquaculture.
Any start works. Neither favor was among the ones the demo marked "Unavailable In Demo Version", and the game's code has no start restriction on Joe Wild's network, so the order is the same whichever scenario you picked. You don't need a new save either: one player's first video with the update (Fruit Newt, October 19, 2026) buys Aquaculture on a save from before it.
What the starter kit contains. In the game's data, buying Aquaculture gives you:
- a Recirculating Aquaculture System and its RAS Water Tank,
- one batch of fertilized Tilapia Roe,
- an Energy Cell,
- a Jug of Water filled with Rustwater,
- two bags of Industrial Fish Feed,
- a Kitchen Knife,
- a Marking Pen.
The Marking Pen "Marks an animal or a fish with a colour. The Auto Butcher never touches a marked animal."
It also books the Retired Aquafarmer's first visit.
Aquaculture II reads: "The retired aquafarmer will also bring bigger, more profitable fish to raise on each visit. Immediately receive two young eels." The two eels are one male and one female.
Setting up the fish tank
The Recirculating Aquaculture System, or RAS, is "A closed water loop for raising fish. Needs a water tank, power, and filters to keep the water clean." Its RAS Water Tank says: "Fill it in place; once slotted it stays with the system."
-
Recirculating Aquaculture System -
RAS Water Tank
- Fill the water tank. The kit's Jug of Water holds Rustwater; our water grades guide explains what each grade of water is. The tank's panel shows how much water it holds against how much the fish need.
- Give it power. The kit includes an Energy Cell, "A basic power source that is compatible with most machines. Rechargeable."
- Add filters. Filters keep the water clean. The Retired Aquafarmer sells a Water Filter on every visit.
- Add fish. Put in the fertilized roe from the kit, or fish you buy.
Watch the status line. Each fish's tooltip warns you when something is wrong: No Water, Low Water, Polluted Water, Toxic Water, Suffocating or Hungry. The tank also shows how much waste is in the water. A fish's tooltip says whether it is "Sensitive to dirty water" or "Unharmed by dirty water", and the Gutter Tilapia's adds "Cleans contaminants from the water": it keeps its own tank cleaner. The Graft Tilapia's description says it needs clean water.
Probably Stolen fish species
There are six fish in the game. The game describes them as follows; diets, breeding and the Sturgeon's sex are from the game's data.
- Tilapia (omnivore, breeds): "Common farm fish. Grows fast, eats most things and breeds without much help."
- Gutter Tilapia (omnivore, breeds): "A sewer strain of tilapia. Grows slower and makes less meat for its feed, but dirty water does not bother it, and it takes heavy metal and chemical contaminants out of the tank while it lives there."
- Graft Tilapia (omnivore, breeds): "A modified tilapia. Makes less meat for its feed and needs clean water, but its skin can be sterilized and used as a bandage, and its unfertilized roe dresses a wound as it is."
- Eel (carnivore, does not breed): "Raised for its luxury fillets, worth far more than any other fish. Does not breed in captivity."
- Electric Eel (carnivore, does not breed): "A living generator. From adolescent on, it charges its tank's battery and every battery beside the tank each night, more as it grows."
- Sturgeon (carnivore, does not breed): "Farmed for caviar." Every Sturgeon is female.
-
Tilapia -
Gutter Tilapia -
Graft Tilapia
-
Eel -
Electric Eel -
Sturgeon
Tilapia roe comes in the starter kit, and the Retired Aquafarmer brings fertilized roe of all three tilapia. The Eel, Electric Eel and Sturgeon only come from him once you own Aquaculture II, or as the two young eels Aquaculture II gives you.
What the Retired Aquafarmer sells. In the game's data, every visit brings a Water Filter, Gutterflow Pellets, Industrial Fish Feed and fertilized roe of all three tilapia. Until you own Aquaculture II, every visit also brings equipment: a spare RAS with an empty water tank, a Livestock Feed Dispenser, an Auto Butcher, a Marking Pen and a Meat Cleaver. After that, each piece only turns up on some visits, and each visit brings three big fish instead, each an Eel, Electric Eel or Sturgeon picked at random.
How to feed fish in Probably Stolen
There are two fish feeds, and neither is food for people.
- Gutterflow Pellet: "Pressed gutter sludge. Cheap calories for omnivore fish, not for people."
- Industrial Fish Feed: "Mass produced factory-made feed for omnivore and herbivore fish."
-
Gutterflow Pellet -
Industrial Fish Feed
Don't feed tilapia only pellets. The pellet's own rule reads "Meat turns trash grade once pellets pass" a share of a fish's diet, and trash-grade meat is "not food". The Gutter Tilapia is the exception: it "Does not suffer a penalty from eating Gutterflow Pellets". Tilapia tooltips can also show that a fish grows faster on meat.
Eels and sturgeon need meat. Both feeds are described as food for omnivore and herbivore fish, and in the game's data the Eel, Electric Eel and Sturgeon are carnivores. A hungry fish shows "Hungry" in its tooltip.
The feed dispenser works for fish too. The RAS has a dispenser slot, and the Livestock Feed Dispenser lists pellets and fish feed as "fish only" calories next to meat. It is the same machine rat ranchers use.
How to breed fish
Only the three tilapia breed. The Eel, Electric Eel and Sturgeon all say "Does not breed in captivity", so you buy more from the Retired Aquafarmer instead.
From egg to adult. In the game's data a fish goes through six life stages: Roe, Fry, Juvenile, Adolescent, Adult and Elder. Roe is either Fertilized or Unfertilized; what the starter kit and the Retired Aquafarmer give you is fertilized. The tooltips count down to each step: how many days until the eggs hatch, until the fry become juveniles, and until the next life stage.
Breeding fish. A female carrying eggs shows "Gravid" and an egg count, and stops growing them while she is badly hurt, until she heals. Unfertilized Graft Tilapia roe is not wasted: it can be used on a wound as it is.
Old age. An elder fish's tooltip shows "Old age: may die any night", so sell or harvest fish before they get there.
Harvesting fillets and caviar
Fish are livestock, like rats: you raise them, then cut them up. The starter kit's Kitchen Knife is for this, and the Retired Aquafarmer also sells a Meat Cleaver.
- Fillets: fish give Tiny Fish Fillet, Small Fish Fillet, Fish Fillet, Large Fish Fillet and Fish Scrap; eels give Small Eel Fillet and Eel Fillet, "A delicacy on the station."
- Caviar: the Sturgeon's "eggs can be harvested using surgery tools while the fish is alive, or collected in full at slaughter." You get Caviar and Sturgeon Roe. The game's surgery tool is the Surgery Toolset.
- Medical products: a Graft Tilapia gives Tilapia Skin Graft, "Sterilized skin of a graft tilapia. Stops the bleeding and closes a wound." Its roe is "Thick with the repair protein that makes the skin heal, which is why medics buy them by the clutch."
- Power: an Electric Eel charges the tank's battery and the batteries beside it every night.
-
Fish Fillet -
Eel Fillet -
Caviar -
Tilapia Skin Graft
How to upgrade the fish tank
The October 19 announcement says you can upgrade the tank if you bring the right materials. In the game's data there are three upgrades, each with a limit:
- Scrap Metal makes the tank wider.
- Metal Ingot makes it taller.
- Electronic Parts (Common) make it use power more efficiently.
Rat ranchers will recognize the first two: the Animal Cage is repaired with Scrap Metal and expanded with Metal Ingots.
Fish or rats: which to farm
The developers' Demo Update - Aquafarmer announcement of October 19, 2026 calls fish farming slower and lower-maintenance than rat ranching, and more beginner friendly.
The two differ in where your stock comes from. Rats breed freely and you can catch them; with fish, only tilapia breed, and the eels and sturgeon have to be bought. Rats live in an Animal Cage, fish need a tank with water, power and filters. Both use the Livestock Feed Dispenser, and both end at the butcher's block. Our rat ranching guide covers the other route.
Version notes and limits
This page describes the full game as released on October 28, 2026 (Steam build 26263409); fish farming first came to the demo in its October 19, 2026 update. That update's announcement showed a new interface for the full release that the demo did not have, so this page describes what to do, not where to click. It gives no power, water, time, chance or calorie figures.
Still open: how the tank's waste relates to the water grades you test for drinking, and whether fish meat has anything to do with rats' Prion Disease. A changed rule is added with the date it was checked.
Probably Stolen aquaculture FAQ
Why can't I buy Aquaculture?
You don't own Water Trading yet. Aquaculture requires it, and the network says "This upgrade requires Water Trading."
Do I need a new save for fish farming?
No. The favor works on any start, and a player bought it on a save from before the October 19 update.
What is in the Aquaculture Starter Kit?
A fish tank with its water tank, fertilized tilapia roe, an Energy Cell, a jug of Rustwater, two bags of Industrial Fish Feed, a Kitchen Knife and a Marking Pen.
What does the fish tank need?
Water in its RAS Water Tank, power and filters. Its description says so, and the Retired Aquafarmer sells Water Filters.
What do fish eat in Probably Stolen?
Tilapia eat Gutterflow Pellets and Industrial Fish Feed; don't let pellets become most of their diet, or the meat turns trash grade. Eels and sturgeon are carnivores and need meat.
Which fish can breed?
Tilapia, Gutter Tilapia and Graft Tilapia. The Eel, Electric Eel and Sturgeon do not breed in captivity.
How do I get caviar?
Raise a Sturgeon and take its eggs with the Surgery Toolset while it is alive, or collect them all when you slaughter it.
How do I make the fish tank bigger?
Use Scrap Metal to make it wider and Metal Ingots to make it taller. Electronic Parts (Common) improve its power use.
Is fish farming easier than rat ranching?
The developers say it is slower, needs less upkeep and suits new players better than rat ranching.
Sources and version history for this guide: Probably Stolen sources and versions.
Spot an error or a post-patch change? See how we label evidence and handle corrections in the Editorial Policy.