Know what your water test means, and what to do next
App-aquatic reads your test results, tells you where your tank's cycle is and when it will finish, and checks every fish before you buy it. Free to download, with a 14-day trial of everything.
Free download
14-day trial, no card
No ads
7 languages
Cycle companion · Premium
Know where your cycle is, and when you can add fish
The nitrogen cycle is where most new tanks go wrong, because the same number means different things at different stages. Log ammonia, nitrite and nitrate as you test, and the cycle companion tells you what they mean.
Names your stage, from Just started to Ready for fish, and counts the days
Estimates the days remaining, and narrows the estimate with every test you log
Separate advice for fishless and fish-in cycles, with an ammonia dose worked out from your tank volume
A final 24-hour test that proves your filter can process a full ammonia dose before fish go in
What the cycle companion tells you
Just started
Building bacteria
Mid-cycle
Nearing completion
Ready for fish
Day 12 · Mid-cycle
Nitrite wave underway - roughly 9 days remaining
Wait ~24h, test again, log again.
Water testing
Read your test in one photo
Photograph your test tubes or strip and Premium Scan reads every value and flags the ones that need attention. Prefer to read it by eye? The offline reader, with preset colour charts for popular kits from API, Tetra, JBL, Sera and more, is free and stays free.
Premium Scan works with liquid kits and test strips
Calibrate your own kit's colours if it isn't in the list
Every reading saves to your history, free
Compatibility checker · Premium
Check the fish in the shop, not after it's in your tank
Add the fish you keep and the one you're thinking of buying. The checker scores every pairing from 0 to 100% and tells you what the problem is, not just that there is one. It runs on your phone without a connection, so the decision gets made at the shop.
Flags fin nippers, aggression and predators big enough to eat their tankmates
Checks that temperature and pH ranges actually overlap
Warns when a shoaling fish is below its minimum group size
Shows how close the tank is to its stocking limit
What the checker tells you
Tiger Barb is marked Semi-aggressive. Watch for fin nipping and territory.
No shared pH range across selected species.
Tracking · Premium
See trouble coming before your fish do
Every test builds a history. App-aquatic watches which way your numbers are moving, not just today's value, so a slow nitrite rise gets caught days before it becomes an emergency.
Plain-language insights such as Nitrite rising and Nitrite may reach 0.25 in ~2 days
Trend charts by week or month, against the ideal range for your fish
Care reminders for water changes, filter rinses and feeding
Fix My Tank · Premium
Something wrong? Photograph the tank and get a 7-day plan
Take a photo of your aquarium and Fix My Tank gives it a health score, lists what it found and builds a plan of daily tasks for the next seven days. Link it to a saved tank and it takes your test history into account too. On day 7, an after photo shows what changed.
Your 7-day plan
D1
D2
D3
D4
D5
D6
D7
Tick off each day's tasks as you go. On day 7, an after photo compares the tank with where you started.
Free forever, with Premium when you want the judgement
Download free and every feature is unlocked for 14 days, no card needed. When the trial ends, the essentials keep working and nothing you've logged is deleted.
Free forever
Offline water test reader with preset kit charts
Kit calibration for your own test kit
Your saved test history
Fish, plant and algae guide: 800+ fish and invertebrates, 175 plants
Tap-water profile, calculators and emergency triage
No ads
Premium
14-day free trial · monthly, annual or lifetime
Cycle companion
Compatibility checker
Fix My Tank 7-day plans
Premium Scan and species photo ID
Water trends and insights
Care reminders
Tank dashboards, photo journal and multiple tanks
Backup and export
Questions before you download
Is App-aquatic free?
Yes. It's free to download, and the offline test reader, kit calibration, your test history and the fish and plant guide stay free, with no ads. Premium adds the cycle companion, the compatibility checker, Fix My Tank, Premium Scan, trends and reminders. Everything is unlocked for 14 days when you first open the app, with no card needed.
What happens when the trial ends?
The free features keep working and nothing you've logged is deleted. The Premium tools lock until you subscribe, monthly or annually, or with a one-off lifetime purchase. There are no ads on any plan.
Does it work offline?
The test reader, the species guide, the cycle companion and the compatibility checker all work without a connection, which matters when you're standing in a fish shop. The photo features (Premium Scan, species ID and Fix My Tank) need an internet connection.
Is it on iPhone and Android?
Yes. The same app is on the App Store and Google Play, for phones and tablets.
Which languages does it support?
English, German, Dutch, Italian, Spanish (Spain and Latin America) and Portuguese (Brazil).
Is it good for beginners?
Especially for beginners. A new tank, a test kit you're not sure how to read and a shop full of fish is exactly where it helps: the cycle companion walks you through your first cycle, and the compatibility checker catches the classic first-tank mistakes before you make them.
Start with your next water test
Download free, log your first reading, and let the app tell you what it means.
