Starsand Island Fish Pond Guide: Oxygen, Eggs & Expansion

A fish pond in Starsand Island is where caught fish turn into eggs, more fish and a trickle of crafting by-products. The system has three pond sizes, an oxygen budget that limits how many fish fit, an incubator upgrade that the Intermediate Angler quest calls “expanding” the pond, and a feed item that triggers egg-laying. This guide puts the numbers in one place and sorts out the two questions that generate most confusion: why the small pond only takes a few fish, and whether you need two of the same species to breed.

Pond recipes, prices and the incubator cost are taken from the game’s machine and crafting data (which already includes Version 1.0 strings); behaviour notes are Early Access player reports, still being confirmed for 1.0. The August 20 hotfix (1.08.3916) only touched a codex display issue for the Stone Fish Pond.

The three pond types

All three blueprints are sold at AquaBlue Outpost (Delphin); the Angler rank in brackets is what you need to see the blueprint.

Pond	Footprint	Oxygen capacity	Blueprint	Build recipe
Small Fish Pond	8×8	12	2,500g (Junior Angler)	Stone Brick 20, Softwood Plank 10, Fiber 20, Copper Sheet 10 — Worktable I
Stone Fish Pond	14×17	12	2,500g (Junior Angler)	Same as Small
Medium Fish Pond	20×20	40	4,500g (Intermediate Angler)	Hardwood Plank 15, Iron Nail 20, Stone Brick 40, Fiber 50 — Worktable II

The Stone pond is a bigger, decorative footprint with the same capacity as the Small one; only the Medium pond actually raises the fish count. Early Access patch notes also mention an “Intermediate Fish Pond” placement fix — that appears to be the Medium pond under an older name.

Oxygen: why a small pond only holds 2–4 fish

Every species has an oxygen value of 1, 3 or 5, and the sum of the values of the fish in a pond cannot exceed the pond’s capacity. With a cap of 12, a Small or Stone pond takes for example:

12 × oxygen-1 fish (Clownfish, Pearl Glowfish, Bitterling, Glowfish (King)…)
4 × oxygen-3 fish (Tuna, Bass, Dolphinfish, Comet Glowfish…)
2 × oxygen-5 fish (Giant Barb, Zander, Paddlefish, Swordfish (King)…) with 2 oxygen to spare
or any mix that adds up to 12

That is the whole “fish pond oxygen” mechanic — it is a per-fish weight, not a resource you top up. The Medium pond’s 40 allows 8 oxygen-5 fish or 40 oxygen-1 fish. Oxygen values for every species are in the fish data; the ones players ask about most are on the rare fish locations page and the King fish table.

”Expand the fish pond” = build the Fish Egg Incubator

The Intermediate Angler quest line reads build a small fish pond → learn to expand it → obtain one fish egg. “Expanding” does not make the pond larger. It unlocks the pond’s second tab, the Fish Egg Incubator, built in place with:

Glass Pane 4 (Quartzite → Glass Brick in Furnace I → Glass Pane at Cutter I)
High-Performance Wire Set 2 (gold-based; see ore locations)
Iron Ingot 4

The cost is identical for all three pond types. Once built, the incubator hatches fish eggs — one egg at a time, 1,440 minutes (one full day) each — into an adult fish that joins the pond.

Fish eggs and Fish Feed

Put a fish in the pond.
Feed it Fish Feed — crafted at Chopper II from Vegetable Juice 1 + Fruit Pulp 1 + Flour 1, five per batch.
Each night there is a chance the pond produces an egg, shown as a small fish icon on the pond.
Move the egg into the incubator tab; it hatches after one day. Eggs can also be kept for the codex, handed in for quests (Intermediate Angler needs one; the Senior Angler trial needs a Giant Barb egg), or used as ingredients.

One fish is enough. Sources disagree slightly here: a well-upvoted Reddit answer states that a single fish will lay eggs and more fish simply means more eggs, while an earlier thread has a user insisting on two of the same species. The single-fish reading is better supported and matches how the incubator behaves, so: one works, several speeds it up. Egg output is slow for some species — one Giant Barb took about ten days in a player’s pond.

Advanced Fish Food (Chopper III: Salt Brick 2, Sugar 2, Flour 1) is not pond food; it goes into the Fish Trap. Bait (Meat/Veggie/Bug) is for casting. Details on the fishing guide.

Pond by-products

Besides eggs, item data marks Fat, Skin, Scale, Hard Scale and Fin as “produced from Fish Pond”. They feed into crafting and cooking recipes and are collected from the pond like any other output. An Early Access patch fixed collection robots ignoring pond products, so robots now pick them up as well.

What to do with fish

Sell them — prices range from 50g (prawns) to 1,607g (Glowfish (King)); the Merchant Ship sometimes buys specific species in bulk at a premium (see money-making guide).
Pond them for eggs and by-products.
Aquarium — the Senior Angler quest asks you to fill the AquaBlue aquarium with 20 species.
Cook / craft — Fish Fillet is the base of Meat Bait.
Gift — a few villagers like specific fish; check the gifts guide.

Early Access bug history (fixed)

If you are reading an older forum thread, these were real problems that have since been patched:

Wooden Small Fish Pond not producing eggs while the Stone pond did (February reports).
Moving a pond left eggs stuck “queued” or stopped incubation (patched 0.3.4631 / 0.4.8191).
Kissing Gourami eggs would not hatch (0.3.3595).
Shrimp could not be placed in ponds (0.5.3241) — note that in current data the three prawn/shrimp species do not lay eggs even though they can be ponded.
Collection robots skipped pond products (0.4.8191).
Version 1.08.3916 (August 20, 2026): Stone Fish Pond now shows correctly in the codex after you obtain it.

Full patch list: updates and patch notes.

FAQ

How do you get fish eggs?

Keep at least one fish in a pond and feed it Fish Feed (Chopper II). Eggs appear overnight as a fish icon on the pond; collect them and either hatch them in the incubator tab or hand them in for quests.

How many fish fit in a small fish pond?

Up to 12 oxygen worth: twelve oxygen-1 fish, four oxygen-3 fish, two oxygen-5 fish, or a mix. The Medium pond allows 40.

How do I expand the fish pond?

Open the pond, go to the second tab and build the Fish Egg Incubator (Glass Pane 4, High-Performance Wire Set 2, Iron Ingot 4). That is the “expand” step in the Intermediate Angler quest.

Do I need two of the same fish to breed?

Player consensus says no — one fish lays eggs, more fish lay more. One older thread claims two are required; treat that as the minority view.

Last reviewed: August 23, 2026 — sources: game machine/crafting data export, official Steam patch notes (EA 0.3–0.5 and Aug 20, 2026), Reddit player reports, player videos.

Was this guide helpful?