How to Grow a Fish in Harpoon a Fish (And What Growth Does)

Growing a fish in Harpoon a Fish takes one action: put the fish you caught into your aquarium. From there it grows over time on its own, getting fat and big as you work toward the biggest, rarest sea monster it can become. Here's how the loop works and what growth actually gets you.

Catch a fish, then place it in your aquarium

First you need a catch in hand. Our how to catch fish guide covers the details, but the short version: aim at your target and fire, then time your reels to pull the fish in. Other players can try to steal your catch mid-fight, so firing first doesn't guarantee the trophy — only a fish you actually land can be grown.

Once the fish is yours, put it in your aquarium. That's the final step in the game's own How-To: "Put caught fish in your aquarium and GROW YOUR NEW PET!" A caught fish goes straight in as your new pet, where it starts growing.

What growth does

Your fish grows in the aquarium over time, and growth changes two things:

• Your fish gets fat and big. Fat drives progress: a fatter fish sinks deeper, and deeper water is where you discover and catch new sea monsters.
• It evolves toward the biggest, rarest form. That's the stated growth goal — evolve your fish and grow the biggest and rarest sea monster you can find. Our fish evolution page goes deeper on that side.

The game pairs the reward with a warning: danger lurks the deeper you go, so a fat fish opens up new hunting grounds, but riskier ones. Everything you discover on the way down fills out your fish index, which tracks over 1,800 unique fish.

Store passes that affect growth

Growth is time-based, and the in-game Store sells two passes that affect it. Prices are as listed at the time of writing:

Both are optional — a fish you place in the aquarium grows without them. For the rest of what the aquarium offers, see our aquarium guide, and the Harpoon a Fish codes page tracks any active freebies.

Quick recap: catch the fish, drop it in your aquarium, and let it grow fat. A fatter pet sinks deeper, and deeper water is where you discover and catch new sea monsters — evolve toward the biggest and rarest you can find.