Fish Ponds: Why and What?

This guide seeks to break down the fish pond: what is it good at, what is it bad at, how do you use it best?

The Basics

A Fish Pond is a 5x5 structure built by Robin the carpenter. It costs stone, green algae, and seaweed, and builds much more quickly than most structures.

A fish pond can hold one type of fish, and only one. It will contain between 1 and 10 fish of that type. A sign (any type) may be placed on the fish pond to show the current fish and population count.

The population of a fish pond increases by one at regular, predetermined intervals. These intervals are set by the species, the fastest breed each day, the slowest every five days. Legendary fish are incompatible with fish ponds.

Each type of fish can produce items. The drop rate and what can be dropped is different from species to species and is frequently dependent on the population: the best drops require a high population, while low populations rarely drop anything at all.

The most common drop is roe, an item whose price is based off the price of the fish (always at base quality). Other drops include gems, ores, geodes, totems, and other valuable goods. A fish pond can produce only one drop per day, but some drops are things like "ten magma geodes" or "two squid ink" so one DROP doesn't mean one ITEM. Drops are lost if not collected by the end of the day.

The Bad

Almost everything you build on the farm is there to make you money. The fish pond is not. The most expensive item a fish pond will give you, Aged Lava Eel Roe, has a base price of 760 and that's after a Preserves Jar gets done with it. A full lava eel pond averages 0.97563091 lava eel roe per day. That's an average of 741 gold per day.

A fish pond is a 5x5 square. That's the same as an iridium sprinkler and all its crops. That's smaller than a chicken coop. Both of those options give more reliable gold output at far less trouble.

A fish pond is cheap to build. But it has iterating costs. Not just gold, specific items that must be provided. That means questing and trusting to luck. Average gold per day of a lava eel pond caps at 486 until you hand it an iridium bar.

So what is a fish pond bad at? A fish pond is bad at making you money. A fish pond is bad at making early gains. A fish pond is bad at land management.

The Good

So why do we want a fish pond?

Achievements. You want full shipment? You'll need roe, and stuff made from the right kinds of roe.

Easy fish. Catching a fish from a pond is 100% automatically successful. Every fish you pull out of a pond lowers its output over time, but they'll breed back up. The fish will only be normal quality, but the community center won't care, and neither will any villager that wants one. Think about that next time Willy asks for an octopus.

Special items. Fish drop more than just stuff you can sell. The best fish, they get you stuff that's crazy useful. How crazy? Prismatic shards, iridium ore, omnigeodes.

The Cost

A fish pond is a remarkably cheap structure. 5000 gold, 300 stone, 5 green algae, 5 seaweed. What's the catch?

The catch is that a fish pond only holds one type of fish. When you throw that first fish in, you set the type of pond (you can reset it later) and, depending on the type of fish, it has a maximum population of one or three.

Fish in a fish pond multiply, even if there's just one fish in it. It takes 1 to 5 days to breed a new fish, again depending on fish type. If the pond tries to breed a new fish but is full, it creates a miniquest: give us this item. The type and number of items are set by the type of fish (often randomly chosen from a list). Until the requested item is provided, the fish pond will not progress further. At ten fish, the pond is at maximum and will not grow further.

For example, a fish pond can only hold one lava eel. Five days after putting that lava eel in it will ask for three fire quartz. Five days after I give it that quartz, the pond will breed a second eel.

The vast majority of fish have a quest at 3, 5, and 7 fish. When the pond reaches 10 fish, it is full and the capacity cannot further increase.

Adding fish to a pond that is breeding does not change the timer. Continuing the above example, after providing the three fire quartz the fish pond will generate a new lava eel five days later. If I add a lava eel to the pond on the second day, then the pond will still generate a new eel three days after that, and will have a total of three eels. If I add two eels to the pond, then on the fifth day it would generate the next quest. There is no way to make the quest happen any faster than that, however.

The lava eel's second quest will be for 1 basalt, 2 diamonds, or a Dwarf Scroll III (the blue one). It will pick one of these three items. There's no advance indication of what item will be asked for and reloading does not help.

The Best Fish

What fish give the best items? Simple.
Super Cucumber
With at least nine, you have a 5% chance at iridium ore. Failing that, amethyst or a guaranteed roe. It's not a super hard catch, either.
You will need
one of (3 Coral, 1 Honey, 1 Oyster, 3 Driftwood, or 3 Refined Quarts); one of (1 Dried Starfish, 2 Emerald, 2-3 Omni Geode, or 2-3 Purple Mushroom); one of (1 Diamond, 3 Gold Bar, 1 Iridium Ore, 1 Jelly, 1 Pickles, or 2 Sea Urchin)

Stonefish
Ice Pip
Lava Eel
With three of these fish you get a 10% chance at five copper, iron, or gold ore respectively. At 9 fish they can also drop geodes, frozen geodes, or magma geodes. Lava eel in particular not only has valuable gold ore and magma geodes, it also gives the priciest roe in the game.
Stonefish you can probably skip, but it follows the same pattern as the other two.
You will need - Stonefish
10 Copper Ore; 5 Earth Crystals; one of (10 Coal or 5 Geodes); one of (4 Copper Bars or 5 Refined Quartz)
You will need - Ice Pip
10 Iron Ore; 5 Frozen Tears; one of (10 Coal, 1 Crystal Fruit, or 5 Frozen Geodes); one of (4 Iron Bars or 10 Refined Quartz)
You will need - Lava Eel
3 Fire Quartz; one of (1 Basalt, 2 Diamonds, 1 Dwarf Scroll III); 2 Mega Bombs; 1 Iridium Bar

Octopus
At 9 fish can drop 3, 10, or 1 omni geodes.
You will need
one of (3 Coral, 1 Honey, 1 Oyster, or 3 Refined Quarts); one of (1 Dried Starfish, 2 Emerald, 2-3 Omni Geode, or 2-3 Purple Mushroom); 1 Green Tea

Rainbow Trout
At 9 fish it gets a 2% chance to drop a rainbow shell. If that fails, 0.1% chance to drop a prismatic shard. That's not a lot, but when are shards ever easy to get?
You will need
one of (3 Coral, 1 Honey, 1 Oyster, or 3 Refined Quarts); one of (1 Dried Starfish, 2 Emerald, 2-3 Omni Geode, or 2-3 Purple Mushroom); one of (1 Diamond, 3 Gold Bar, 1 Iridium Ore, 1 Jelly, or 1 Pickles)

Sturgeon
It only ever drops roe, and the only thing more fish does is get you more roe. But this roe becomes caviar, which you need for certain things. Worth holding onto, at least for a little bit.
You will need
1 Diamond; one of (1 Jelly, 2 Maple Syrup, or 1 Pickles); 3 Omni Geodes; 1 Nautilus Shell

Second String Fish

These fish all drop something that might be useful, but either not useful enough or not often enough.

Midnight Squid
Squid Ink is only gained from killing squid kids or putting some kind of squid in a pond. Midnight squid is the better of the two, averaging 1.2 ink a day. It's probably better to hit the mines.

Sunfish
Small chance of a solar essence, otherwise just roe. Cheap roe.

Blobfish
Decent chance at Farm warp totems and a decently pricey roe. Worthless once you get the scepter.

Void Salmon
Decent chance at void essence and even a void egg, but buying the egg is probably better.

Slimejack
Slime. Lots of slime. Lower maintenance than a slime hutch, but the rates aren't great.

Ghostfish
Quartz! Glorious quartz! A crystalarium's better.

Crab Pot Fish
The freshwater stuff gets you mountain totems, saltwater gets you beach totems, and both get you a tremendous amount of trash. Mussel and periwinkle breed quick, if you also want "any fish" for fertilizer and sashimi. Almost certainly not worth it, especially once you can build obelisks.

The Math: Drops

A fish pond makes a check each day to see if the pond might produce something. Across all fish, that check has a probability of .15 + (population * 0.08)

With one fish, that's 15%, or once every week or so. With ten fish, the maximum, that's 95%, or nearly every day. If this check doesn't pass, nothing drops, regardless of the next set of checks (which would not happen if the first check fails).

After that first check passes, the game makes a series of checks that are different for each fish. Sometimes it's easy; a salmon pond has a 90% chance to drop one salmon roe. Sometimes it's trickier; tuna has a 100% chance of dropping roe if there are at least 5 tuna, or only 70% chance if there is less than five.
Each possible check has a minimum population and the game runs each check for the population the pond has until it either passes a check, and thus the pond drops that item, or until it runs out of checks and thus drops nothing.
That's right, a pond can pass the first check and still drop nothing. Both the fist overall check and one of the second checks must pass.

Example, a lava eel pond has nine fish in it. It first needs to pass a 87% check or it drops nothing. Let's say it passes. It now goes down the list.
The first check for 10 magma geodes calls for 10 lava eels. We don't have that, so it skips that check. But 9 fish unlocks the next one, 5 magma geodes, with a 2% chance. If that passes, the game produces the five geodes and is done. If it fails, it moves onto the next line, 5 Spicy Eel. The 7th line, 100% chance for 1 roe, has a minimum 6 fish, and guarantees a drop. The 8th line, 80% chance for 1 roe, will never run unless the pond has less than six fish.

The Math: Breeding Fish

A fish pond that has at least one fish in it will multiply up to its current maximum population, but slowly. The rate is fixed, with no random elements, but different for each fish.

The carp, herring, sunfish, periwinkle, mussel, and anchovy are the fastest. They generate a new fish every day.
The stonefish, ice pip, and lava eel are the slowest. They generate a new fish every 5 days.

You can use any rod to remove a fish from the pond. Doing so is automatically successful, no minigame, consumes no bait or tackle durability, gives no experience or achievement progress, DOES require energy, and ALWAYS generates a basic, no-quality fish.

With this in mind, the fish pond is far too big for the sale value of fish to justify. The only exception is if the fish in question is a crafting ingredient. The only "fish" used in a crafting recipe is coral, which grows at a rate of 2 days.
Midnight Carp (4 days), Flounder (3 days), and Sea Cucumber (2 days) are the only fish used in cooking recipes that come close to justifying the footprint. Frankly, seafoam pudding is not worth three fish ponds (you'll also need one for squid).

In general I do not recommend ever fishing from a pond unless it's to answer a delivery quest.

When a Pond Reaches its Cap
Or if a pond reaches its soft cap. Let's say your Super Cucumber Pond hits 7 fish, then 4 days later it asks for jelly. You do not actually have any jelly. The pond will remain stuck where it is until it gets jelly. Or, you can fish out the seventh cucumber. On the next day, the cucumber will breed again (they already waited the 4 days since the last breeding) and ask for jelly again. This time if you remove the seventh cucumber it will be a full 4 days before the quest returns. But once you get that jelly, you'll be able to take those cucumbers you fished out and drop them right back in that pond. In this way with a little bit of help, the pond continues to grow its potential population even if you can't provide the item it needs. This trick is especially useful if it's asking for something rare like a specific mineral or iridium.

The Math: Timing Quests

The behavior of fish ponds regarding the soft caps and quests is a little unusual. Completing a quest to expand the capacity resets the growth timer, but adding or removing fish does not. Further, the quest is generated when a full pond tries to generate a new fish and cannot. Such a fish pond has its growth timer stuck at one day. A generated quest is available to complete whenever the population is at the current maximum.

This collection of facts makes the fastest growth rate thus: when a fish pond generates a quest, remove a fish from the pond. The next day, the fish pond will create a new fish, allowing you to finish the quest and re-add the previous day's fish. This can save you nearly a full cycle of growth.

Say we have an ice pip pond, breeding once every five days.
We start counting time on the first day there are six ice pip: this is Day 0.
Day 5: The fish pond breeds to 7 fish (its current maximum)
Day 10: The fish pond generates a quest for either 4 iron bars or 10 refined quartz. Let's assume it's iron bars.

The Obvious Approach
Day 10: The player tosses 4 iron bars into the fish pond
Day 15: The pond grows to 8 fish.
Day 20: 9 fish
Day 25: The pond reaches its final maximum of 10 fish.

The Manipulative Approach
Day 10: The player removes an ice pip from the pond. The population is now 6, the quest vanishes.
Day 11: The pond grows to 7 fish. The quest reappears. It is always the same quest: if it was 4 iron bars before, it will not switch to quartz now. The player adds the iron to the pond. The player adds the ice pip from Day 10 to the pond. The pond now has 8 fish.
Day 16: 9 fish
Day 21: The pond reaches its final maximum of 10 fish.

[Motherlander]

Apologies if this was mentioned earlier, but a maxed out Crab Pond, while not very valuable by itself, will cause Willy to gift the player a Pearl. I think this happens once only per farm.

[thedemoman3000 #SaveTF2]

you forgot to mention that lava eels give you spicy eels which can be nice. also fish ponds cost 200 stone. not 300

[Techhead7890]

The Stingray from Ginger Island is worth doing too. 23% daily chance for a Battery, Cinder Shard or Dragon Tooth!

[Ryvaken Tadrya]

Bluemonkey: The fish pond consumes 25 squares of buildable land. The peach tree consumes 9. You can fit almost three trees in the same amount of space as a single pond.

Also, fruit trees are notoriously poor investments. If it were not for the greenhouse, they would be nearly useless. There are no locations you can build a fish pond but not something else.

[bluemonkey]

Fish ponds are a reasonable alternative to fruit trees in terms of early game financial returns. Consider flounder--readily available early game with some effort put into ocean fishing--it is worth 100g, breeds every 3 days and produces roe worth 80g about every other day. In the course of a year, roe would generate 80g x56 = 4480 g/year and excess flounder sold at 100g x 37.3= 3733 g/year. This is 8213g after investing 5000g in a fish farm + stocking. Starting from a single fish, it will take slightly less than a month to reach steady roe production and another two weeks to reach sustainably harvestable fish--flounder only need to have a population of 5 to produce roe at maximum rate. Once fully setup, this is 73g/day.

Consider a peach tree: the sampling takes 28 days to mature and then within its first year, it will produce peaches for 28 days worth 140g. This is 3920g after investing 6000g for the sapling. Averaged out across the whole year, this is 35g/day-less than half!!

[Alex-182]

There's no need to, squeakandme.

Regarding that specific aspect you were wondering about, fortunately, you have quite a good source of information here, thanks to Ryvaken, which have done a great job for an unknown feature of the game, a consecuence (IMO) of the low benefits the pond provides compared to other alternatives.

What many players don't know is... if you don't like, for example, the dungeon mechanism and want to play on Zen Mode, you can try (with a modest drop rate though) to obtain certain items (like Prismatic Shard) with this feature, which would be extremely hard to achieve otherwise, because some of them strongly relay on the dungeon system.

Cheers!

[Ryvaken Tadrya]

I've added a Basics section at the top of the guide to clarify Alex's points. Apparently I never did actually write down that the drops from fish were dependent on how many fish you had, rather than just the rate at which drops occur.

[squeakandme]

Thank you for the offer Alex. I got a list of what can drop and at what population levels from the Wiki, but what the wiki did not help me with was knowing why my ponds produced nothing, even after the fish started multiplying. Ryvaken Tadrya's break down of the math clarified that for me.

[Ryvaken Tadrya]

"- Drop rate doesn't scalate with the pond's population, the drop's quality does."
Read the section on the math again. The chance for ANY drop to happen is based on population. The quality of what can drop is ALSO based on population.

[Alex-182]

Hey @squeakandme, maybe I got you wrong (english is not my native language) but I guess you think that every "copy" of a fish inside the pond would increase the chances of getting its drop, but it doesn't work like that.

AFAIC, you only have a (small) chance of getting them when population inside it is 1, 3-4, 9-10, and with 1 you would mostly get regular items.

The good new is that every fish (except one specific "type") is capable of multiply itself, even if there's just one "copy" of it inside the pond (yeah, you've read right). So you could build a lot of ponds and fill them with just one copy of the fish you want its drop from. Be aware that some species need A LOT of time to reproduce.

tl;dr:

- Drop rate doesn't scalate with the pond's population, the drop's quality does.
- The drop rate of the best items it's extremely low, though I can tell you I've got things like a Prismatic Shard and Pearl (several times).

If you want a full list of the drop for every fish let me know.