The Underwater City in Fish It has received a big update with new content, and one of the biggest discoveries is a new secret fish, the Mutant Runic Koi. This fish is part of a limited-time event, so knowing where to go and what to do is important. In this guide, you will find everything needed to get the Mutant Runic Koi in Fish It Roblox.

What Is the Mutant Runic Koi in Fish It?

The Mutant Runic Koi is a new secret fish in Fish It. It only appears during a special Group Fishing event. The cool thing about this fish is that your personal luck doesn't matter much. What matters more is how many players are fishing at the same time.

The more people fishing together, the higher the chance of the Mutant Runic Koi showing up. So this one is a team effort.

How to Get the Mutant Runic Koi in Fish It

Step 1: Wait for the Group Fishing Event

The Group Fishing event runs on a fixed schedule. It repeats every 4 hours. You just need to show up when the event is live and start fishing.

Mutant Runic Koi Fish It

Step 2: Fish With Other Players

Once the event starts, head to Underwater City, cast your rod and fish alongside as many players as possible. Just keep fishing. The secret fish chance goes up the more players are participating, so don't leave early.

Step 3: Use the Atlantis Machine Booster

This is actually a good strategy. Before the event starts, head to Underwater City POI and find the Atlantis Machine. You can donate fish to earn points, and those points give you temporary boosts like:

Atlantis Machine Fish It

  • Luck boost — better chance at rare fish
  • Big Catch boost — helps you reel in bigger fish
  • Shiny boost — increases shiny fish chances

The boosts last between 30 minutes and 1.5 hours, so time it right before the event begins.

So, make sure to keep an eye on the event timer so you know when the next session starts and can plan ahead. It also helps to bring friends, as having more players increases the chances of spawning the Mutant Runic Koi. Before the event begins, consider using the Atlantis Machine to stack a booster for better results. Getting the Mutant Runic Koi in Fish It takes a bit of patience, but it's totally worth it! If you want codes to redeem, more tips, or game information, you can visit our dedicated Fish It wiki.