≋ Tide
How to Play Aquarium
Aquarium is a logic puzzle where you fill water into a grid of tanks. Number clues along the edges say how many water cells each row and column holds — and inside every tank, water behaves like water: it settles level and rests at the bottom.
Our daily version is a 7×7 grid. Every puzzle has exactly one solution, and gravity does half the reasoning for you. This guide covers the rules and the techniques that crack any board.
The rules
- Fill water cells so that every row and column contains exactly the number of water cells shown by its clue.
- Water obeys gravity inside each tank: each row of a tank is either completely full or completely empty, and full rows sit below empty ones.
- Set a tank's waterline by clicking: everything in the tank at that level and below fills, everything above stays empty.
Solving techniques
1. Water finds its level
Inside one tank, a single cell is never wet alone: if any cell of a tank row is full, the whole tank row is full, and so is every tank row beneath it. Read each tank as a set of possible waterlines, not as independent cells — a wide tank's bottom row is often forced just because the column clues can't afford the rows above.
2. Count the clue arithmetic
Compare each clue with what's already placed. If the remaining water a row needs equals the row's undecided cells, they're all full; if the clue is already met, the rest are empty. A 0 empties its whole line instantly, and a clue equal to the full length fills it — always harvest these first.
3. One click decides a whole column of the tank
Marking a single cell full drags every cell below it in the same tank full too; marking a cell empty drains everything above it in that tank. So test cells at the extremes: the top row of a tall tank being full, or its bottom row being empty, usually blows past a row or column clue somewhere — which fixes the waterline.
4. Cross-reference rows and columns
The strongest deductions come from combining both directions. When a row clue forces part of a tank full, gravity extends the water downward, which spends water from the column clues below — often emptying other tanks in those columns. Alternate sweeps: rows, then columns, then back.
Frequently asked questions
What is an Aquarium puzzle?
A grid-logic puzzle divided into tanks. You fill water so every row and column matches its number clue, while water inside each tank stays level and rests at the bottom — gravity is a rule, not decoration.
What do the numbers around the grid mean?
Each number counts the water cells in its row or column. They constrain the whole board at once: a tank's waterline must satisfy every row and column it passes through.
Do Aquarium puzzles require guessing?
No. Every daily board has a unique solution reachable by pure deduction — gravity plus the clue arithmetic is always enough. Difficulty ramps through the week: Monday gentlest, Sunday hardest.
Is it free to play?
Yes. The current week's puzzles are free, no account needed. An account only adds cross-device progress sync — it never gates play.