Aquarium
Pour water into each tank so every row and column count fits.
How to play Aquarium
The grid is divided into bold outlined tanks: the aquariums. Every cell is either water or air, and inside each tank the water behaves like real water: it lies flat, so a whole row-segment of a tank fills together, and it sinks, so anything below a filled cell in that same tank is filled too. In short, each aquarium fills from the bottom up to one level line. The numbers along the top count the water cells in each column, and the numbers down the left count them in each row. Click a cell to set that tank's water line at that row (filling that row and everything beneath it in the tank) and click a water cell to lower the line. Match every clue to solve it, and race your best time.
Think like water
The whole puzzle turns on one idea: inside any tank, water can't hang in mid-air. It lies flat and it sinks. If one cell of a tank holds water, every cell below it in that tank holds water too, and its whole row-segment inside the tank fills at the same time. So each aquarium ends up filled from the bottom to one flat line. Pick the level, and everything else follows.
The classic beginner mistake is treating cells like Sudoku squares, independent little boxes. They're not. A tank is one object with one dial, its water level, and every deduction you make should be about that dial.
That physics is what makes the numbers solvable. A column clue counts the water cells stacked in that column, across every tank it passes through. A row clue counts them along its row. Your job is to set each tank's water line so all the counts come out right at once. Click a cell to set the line at that row (filling it and everything beneath it in the tank), and click a filled cell to drop the level back down.
Where the first moves come from
- Chase the extremes first. A clue of 0 means every cell in that line is air. A clue equal to the line's full length means every cell is water. Both ripple straight into the tanks that cross them.
- Air pushes up, water pulls down. Prove one cell is water and everything below it in that tank fills. Prove one cell is air and everything above it in that tank empties.
- A tall tank has only a handful of possible levels. Test each level against the row and column counts, and often just one survives.
- Watch part-filled lines. Subtract the water you've already placed from a clue, and whatever remains must fit in the tanks still open along that line.
- Wide tanks are the power plays. One decision about a wide tank settles a whole band of cells across many columns at once.
A worked tank
Here's the kind of chain the whole game is made of. Picture a tank two cells wide that spans rows 3, 4 and 5. It has exactly four possible states: empty, water in row 5 only, water in rows 4 and 5, or full to the top. Now suppose the row 5 clue is already satisfied by tanks elsewhere in that row. Then this tank's two cells in row 5 must be air. That single fact kills three of the four states at once, because water sinks: any water anywhere in this tank would have to include row 5. The tank is empty. Six cells settled by one count, and the two columns above it just got easier too.
The mirror case is just as strong. A row clue equal to the row's full length makes every cell in it water, and each tank crossing that row instantly fills everything below that line inside itself. One full row can drag half the board down with it, which is why the extreme clues are always your opening moves.
That's the rhythm of Aquarium: level by level, never cell by cell. When you're stuck, don't stare at single squares. List a stubborn tank's possible levels, count what each level would add to its rows and columns, and cross off every level that breaks a clue. Usually one survives, and the board moves again.
No luck in the tank
Aquarium is a modern logic puzzle in the row-and-column counting family, a cousin of Nonograms, the Japanese picture-logic puzzles that took off in the late 1980s, and of Solitaire Battleships. It's a young puzzle as these things go, spread by puzzle websites rather than newspapers, and it earned its place fast: the rules take ten seconds to learn, and the deductions feel like physics homework in the best possible way. Like its cousins it contains no luck at all. Every water line can be deduced, so a wrong board always means a missed deduction, not a bad break. That's the charm. Clicking a tank to its right level and watching the counts fall into place has the tidy payoff of draining a real tank to exactly the mark. Match every clue and the puzzle is done. Then go chase a faster time.
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Aquarium: frequently asked questions
How does the water fill an aquarium?
Water always settles to a flat level and fills from the bottom up. Within a single tank, if one cell in a row holds water then the whole row-segment of that tank does, and every cell of the tank below it is filled as well.
What do the numbers around the grid mean?
Each number on the top is the total count of water cells in that column, and each number on the left is the count for that row. Fill the tanks so every one of those counts is met exactly.
How do I lower the water in a tank?
Click a cell that already holds water and the tank's level drops to just below it, emptying that cell while keeping the water beneath. Clicking an empty cell raises the level up to that row instead.
Is Aquarium free to play?
Yes. Aquarium runs free in your browser with no download and no sign-up, in a clean, minimalist style, with fresh solver-verified boards every game.
Why does filling one cell fill others?
Water inside a tank lies flat and sinks. Fill a cell and everything below it in that same tank fills, along with the rest of that row-segment of the tank. Each aquarium fills up to one level line.
What do the numbers around the grid mean?
The number on the left of a row is how many water cells that row holds; the number above a column is how many it holds down that column. You set the tank levels so every one of those counts is met.
How do I lower a water level I set too high?
Click a filled water cell in the tank and the line drops to there, emptying the cells above it in that tank. Clicking an empty cell higher up raises the line instead.
Where's the best place to start?
The clues of 0 and the clues that equal a line's full length. They fix whole rows or columns as all air or all water, and that certainty spreads into every tank passing through.
Is guessing ever needed?
No. Every water line follows by logic from the clues and the fill-from-the-bottom rule, so if you're stuck there's a deduction waiting, not a coin to flip.
Can water flow between tanks?
No. Every tank is sealed. Its water level is its own business, and filling one never spills into a neighbour. The tanks only talk to each other through the row and column counts they share.
Is Aquarium free to play?
Yes. Aquarium is completely free on Inkplay, with no download, no sign-up, and no in-game purchases. Open the page and play instantly on desktop or mobile.
Can I play Aquarium unblocked?
Yes. Aquarium runs entirely in your browser with no download, install, or plugins, so it loads instantly and keeps working even on school or work networks where bigger game sites get blocked.
More games to play
In the mood for more? Try 2048, Memory Match, Lights Out, Minesweeper, or browse all puzzle games and the full games list on Inkplay. Aquarium also appears in Logic Puzzles.