Sudoku technique guide

Turbot Fish Sudoku Technique

A Turbot Fish is a single-candidate chain pattern based on strong links. This guide explains the idea in plain English, when to look for it, and the common mistake to avoid.

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At a glance

Difficulty

Hard

This is where Turbot Fish normally sits in a human solving path.

Family

Visual chain techniques

It belongs to the visual chain techniques group of Sudoku logic.

Main action

Usually remove candidates

Most technique moves reduce notes first. That often reveals a simpler placement afterwards.

What is Turbot Fish?

A Turbot Fish is a single-candidate chain pattern based on strong links.

The important thing is that this is logic, not guessing. You are using the current candidates to prove that a number must either go in one place, or cannot stay in another place.

In SudoSketch, this technique is designed to work with notes and Coach highlighting, so the key cells and removal cells can be shown clearly.

How Turbot Fish works

Focus on one candidate.
Find two strong links connected by a weak relationship.
The chain proves at least one end is true, removing the candidate from cells that see both ends.

When to look for it

Look for Turbot Fish after easier moves have stopped working. First check for naked singles, hidden singles, locked candidates and simple pairs. If those do not move the puzzle forward, this technique may be worth checking.

For learning, do not try to scan for every advanced technique at once. Pick one method, understand the shape, and practise spotting that one pattern.

Common mistake

Stay on one candidate. Turbot Fish is not a mixed-candidate chain.

If you are unsure, rebuild the candidates first. Bad notes create bad logic, and Sudoku will absolutely punish you for it like a tiny spreadsheet goblin.

Turbot Fish FAQ

What is Turbot Fish in Sudoku?