Cycle simulation
Watch the nitrogen cycle establish itself and learn why patience keeps fish alive.
For macOS & WindowsA living aquarium,
A living aquarium,
simulated down to the bacteria.
€4.99 per monthmacOS and Windows. Cancel any time, no in-app purchases.
For macOS and Windows.
Every tank tells a story. Now you can watch it unfold.
Sakagotchi simulates a real aquarium — water chemistry, the nitrogen cycle, plants, light and fish behaviour. Plan your next tank before you buy a single fish, or keep a calm little world running on your screen.
Realchemistry: ammonia, nitrite, nitrate, pH and temperature.
Livingfish with schooling, hunger, stress and personality.
Always onRuns as a calm ambient window or screensaver.
The simulation
Design it. Cycle it. Stock it.
Weeks of real aquarium chemistry play out in minutes, so the mistakes happen on screen instead of in your living room.
Pick a tank
Choose a size, substrate and hardscape. Volume and surface area shape everything that follows.
Nano30 L · Shrimp, snails, a few tiny fish
Community120 L · A planted tank with a small school
Show tank400 L · Room for a centrepiece fish
Features
Everything a tank does. Nothing it costs.
Compatibility checks
Mix species and see temperament, size and water needs play out before it happens for real.
Plants & light
Photoperiods, CO₂ and nutrients drive plant growth — and algae if you get it wrong.
Desk companion
Leave it running. Your fish remember you, and the tank evolves while you work.
Desk mode
Leave it running.
As a calm window beside your work or a screensaver, the tank keeps living. Your fish learn your schedule and greet you in the morning.
Pricing
A whole aquarium, for less than fish food.
One subscription, every species and every tank size.
€4.99per month
macOS and Windows. Cancel any time.
- Every species and plant in the simulation
- Unlimited tanks and saves
- Water chemistry and fish health in real time
- No in-app purchases
Our promise
A calm game, kept calm.
- No in-app purchases
Everything is included in the subscription.
- No punishing timers
Your tank waits for you; fish don't die while you're away.
- Cancel any time
Keep your saves if you come back.
I kept a real tank for years and loved the planning more than anything: what lives together, what the water needs.
Sakagotchi is that planning, with a living tank at the end of it.
FAQ
Fishkeepers ask.
Is it a game or a simulator?
Both. Plan a real tank with real chemistry, or just keep a peaceful one running. There's no score to chase.
How accurate is the chemistry?
The nitrogen cycle, pH, temperature and oxygen are modelled per tank. Early testers who keep fish help us tune each species.
Can fish die?
Yes, gently. Sakagotchi warns you early, explains what went wrong, and lets you rewind a day.
Which platforms?
macOS and Windows first, with a desk mode and screensaver on both.