Breeding and mutation

Fish come from two kinds of breeding. Copying makes more of the fish you already have. Mutation turns a pair into a new species. Copying happens in both the Spawning Basin and the Ecotone; mutation happens only in the Basin.

Pairs#

Every breeding needs two fish. Two of the same species breed with no help. Two different species breed only when a mutation crosses them, and only while that mutation's catalyst is in the Basin.

Breeding never uses the pair up. You keep the parents and gain the young, so one pair is the seed of a whole line.

Mutation#

A mutation is a recipe with four parts: a parent, a partner (often the same species as the parent), a catalyst and a chance. Put the pair in the Basin with the catalyst in its slot and some fish food, and every breeding rolls that chance.

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5% a breeding

A worked example. Two cod and an iron nugget give a Ferric Cod with a chance of 5% per breeding. That is one success in about 20 breedings, which at the base tier takes about 200 s.

• Each breeding eats one fish food: wheat, a carrot, a potato, a beetroot or Fish Meal, whether or not the roll succeeds.
• The catalyst is used up only on a success. A run of failures costs food and time, not catalysts.
• A mutation always gives one fish. You need two of the new species to start a line, so expect to mutate twice.
• Without a catalyst the pair can still make copies, but at 25% of the usual speed.

Rarer fish have lower chances and costlier catalysts. A Diamond Ray needs a block of diamond and succeeds 1% of the time, so expect about 100 breedings per success. A tier kit on the Basin shortens each breeding; see its upgrades.

Crossing two species#

Most fish beyond the first few come from two different parents. Here the pair is mixed, so it does nothing until you add the catalyst, and it has young only when the mutation succeeds.

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3% a breeding

Order does not matter: either parent can go in either slot. Because crossing needs two of each parent, a line two steps deep means farming up a pair of each ancestor first.

Tier-gated mutations#

A mutation can name the lowest tier kit the Basin needs before it rolls. Below that tier a mixed pair waits and the screen names the kit, and a same-species pair carries on making copies with a warning that the mutation needs the kit. Enthalpy's own mutations do not use this, but modpacks can; see custom fish.

Why resource fish copy themselves only sometimes#

A vanilla fish copies itself every breeding. A resource fish breeds in the Ecotone and either makes another fish or yields its resource, so it copies itself only part of the time.

A worked example with Ferric Cod. Each breeding there is a 9.91% chance of another Ferric Cod. Otherwise there is a 66% chance of an iron nugget. So a pair makes about 0.59 nuggets per breeding, and a new fish about once in 10 breedings.

The trade-off is plain. If every breeding also made a fish, you would grind the spare fish for their resource and the farm would pay for itself with no limit. Instead each species copies just often enough that grinding the spares adds about half as much again to what the yields give. Each ground Ferric Cod gives 3 nuggets, so 0.3 nuggets per breeding come from copies, about half of the yield figure above.

The rule behind it: the more a fish is worth when ground, the less often it copies itself. A Ferric Cod copies 9.91% of the time; a Diamond Ray only 0.5%. Each species page gives its own chance.

Planning a line#

1. Pick the target. Find it in the breeding explorer and read its line back to the four vanilla fish. Untick mods your pack lacks to see what you can make.
2. List the catalysts. Each step needs one, and the expensive ones come late. Gather enough for the expected breedings, not the best case.
3. Build from the root. Mutate each early fish twice. Keep the pair of each ancestor you will need again.
4. Farm the middle. Put a spare pair of an ancestor in an Ecotone to keep the line stocked; the young land in its fish output, ready to go back to the Basin.
5. Finish at the Basin. Cross the final two ancestors with the catalyst, and move the new pair to an Ecotone.

The Basin and Ecotone both accept pipes and auto-output, so a long mutation run can be left alone. Rare mutations are worth a spare Basin on a tier kit.

Roughly one in 100 of the young is Prized, which pays back along the way.