K-9 math aquarium
Play Mathematical Trout, a K-9 math aquarium game where correct answers earn coins for fish, tanks, food, and koi.
Current Aquarium: Starter Aquarium
Earn
Addition
2 + 3 = ?Addition
Correct answers earn coins for fish and tanks.
Care
Your fish grew too big for this tank. Choose a tank debt or release fish.
Decor
Build a planted habitat with bottom pieces, floating pieces, and animated lights.
Shop
Supplies
Exclusive
Enter the one-time code from a listed koi to bring it into this aquarium.
Ranked
Studio
Design skins for normal fish only. Pick one or more fish, and the price adds up by fish rank.
Style upgrade: +0 coins per fish
Saved
Live
Community
For grown-ups
A parent PIN protects saves, deletion, privacy choices, public sharing, and learning-level choices without blocking normal math play.
The PIN is stored only as a protected verifier on this device. It cannot be displayed or recovered. If it is forgotten, clearing this game's site data removes the lock but also removes device-only aquariums.
Analytics choice has not been set.
On this device
Review progress and choose the learning level for each local aquarium. Nothing here is posted publicly.
Play offline
Add the full web app to this device. No separate download is needed, and aquarium progress remains saved on this device.
Installing websites as apps requires macOS Sonoma 14 or newer.
If Add to Dock is missing, open this same website in Chrome or Edge instead.
You can also select the install icon in the address bar when it appears.
Open Mathematical Trout in Chrome or Edge, or use Safari on macOS Sonoma 14 or newer. You can keep playing here without installing.
Look for Install app or Add to Home Screen. You can keep playing here if your browser does not include that choice.
Koi Coach
Skill: Number sense and computational fluency.