Breeding toward a resource
Plan a breeding line to the fish that yields what you want, and get there without wasting catalysts.
1. Find the line#
Type the resource you want into the breeding explorer, for example gold. It finds the
Gilded Koi and lights its line: a 
Ferric Cod and a
Cupric Salmon, each bred from base-game fish, then crossed with gold as the
catalyst. Note the catalyst for every step before you start.
2. Breed each step twice#
Each mutation gives one fish, but a pair needs two. So for each step:
- Load the Basin with the step's parents, fish food and its catalyst.
- Keep it running until two of the new species have come out. Each success uses one catalyst, so have a few ready.
- Move the pair on to the next step's Basin, or to an Ecotone.
Two different fish only breed together while the catalyst of a mutation that crosses them is in, so a crossing step never wastes time on copies.
3. Speed it up#
- Run several Basins at once, one per step.
- Fit tier kits: a Harmonic Basin breeds ×4 as fast as a bare one.
- Farm each step's species in an Ecotone while you climb: a pair of Ferric Cod yields iron the whole time.
Pitfalls#
- Resource fish copy themselves only sometimes, rarer ones very seldom, so don't plan on a Basin making you a second rare fish by copying. Mutate twice.
- Without a catalyst for any of its mutations, a Basin breeds at reduced speed.
- Some fish only exist with other mods installed; the explorer fades them when you untick a mod.