Harpoon a Fish Fish Evolution: What Evolving Does and How to Get a Fish Ready

Fish evolution in Harpoon a Fish works on fish you've caught and housed in your aquarium — never on wild sea creatures still in the water. The game's own pitch says as much: "EVOLVE your fish and grow the BIGGEST and RAREST sea monster you can find!"

Getting a fish ready to evolve

Evolution works on housed fish, so preparing one is the catch-and-raise pipeline:

1. Aim at a sea creature and fire your harpoon.
2. Time your reels to pull the fish in.
3. Put the caught fish in your aquarium.
4. Raise it as your new pet — housed pets are the fish that can be evolved into bigger, rarer monsters.

If the harpooning half is where you're stuck, our guide to how to catch fish covers aiming and reeling in detail. Once your catch is in the tank, the aquarium guide picks up the raising side.

What evolving your fish does

Evolving turns your housed catch into a bigger, rarer monster — officially, "the BIGGEST and RAREST sea monster you can find." Evolving is part of raising that pet, not a separate activity: caught fish are raised as new pets in the aquarium, and evolving them into large, rare beings is part of that raising.

With over 1,800 unique fish to fill out your index, there's no shortage of catches to bring home and house.

Growing and evolving

The game presents growing and evolving as linked parts of your fish's development. Growing means getting fat and sinking deeper to discover and catch new sea monsters; evolving turns the pet already in your tank into something bigger and rarer. Treat raising your fish as one continuous project and keep developing your pet — our how to grow fish guide covers the day-to-day raising.

While you work on the raising side, codes give free EXP and Ruby Keys that boost your progress fast — check our Harpoon a Fish codes page before a long session.