Tap the + button on the Tanks tab. Enter a name, pick a water type, enter the volume in your preferred unit, and optionally set the setup date and substrate. Enable "Add starter maintenance schedule" to get sensible recurring tasks pre-loaded for your tank type.
Support
Gillwise Support
Help for Gillwise 1.1 — aquarium care companion for iPhone and iPad.
Inside a tank, tap "Log water test" in the Water tab, or use the ··· menu at the top right. You only need to enter the parameters you actually tested — Gillwise grades whatever you log and skips the rest. Tap any logged reading to see the full parameter-by-parameter verdict.
In the Water tab, tap the circular-arrow button next to "Log water test." Pick the parameter you want to correct, enter your current reading, your target, and your tap/source water's value for that parameter. Gillwise shows the exact percentage and volume to change and predicts the result. For large corrections (over 40%), a 3-step gentle plan is offered.
In the Water tab, tap "Export CSV" (appears when you have at least one logged reading). This creates a spreadsheet file with all your readings in date order, including every parameter and your notes. Share it to Files, AirDrop, email, or any compatible app.
The Health tab contains an offline reference for 12 common diseases and conditions. Search by symptom (e.g. "white spots") or name, and filter by freshwater, saltwater, or severity. Each entry lists what you'll see, what causes it, first response steps, and prevention — no internet needed.
In a tank's Stock tab, tap "Add livestock or plants." You can filter the 145-species library by kind (Fish, Invertebrates, Plants, Corals) and search by name or region. Tap + to add each species, then tap Done. The bioload gauge and compatibility checker update immediately.
The Stock tab's Compatibility section automatically checks your mix for fin-nippers paired with long-finned fish, predators with small prey, shoaling species kept in too-small groups, water-type mismatches, and overlapping temperature or pH needs. A yellow triangle on a species row means it's involved in at least one issue.
Email the App Store product page with your iPhone model, iOS version, and a short description of what happened.
Common Questions
Does the app require an account or internet?
No. Gillwise is fully offline. No sign-in is required, and no data leaves your device.
What parameters can the water change calculator correct?
Nitrate, pH, General Hardness (GH), Carbonate Hardness (KH), and Salinity. The list adjusts to your tank type — GH is shown for freshwater, Salinity for marine.
My source water has a higher nitrate than my tank. What should I do?
If tap water nitrate exceeds your target, the calculator will flag that a single change can't reach the target and explain why. In this case, using RO/DI water (nitrate ≈ 0) for water changes is the standard solution. Enter 0 as the source value if you're using RO/DI.
Why does the Water tab pre-fill values in the calculator?
When you have at least one logged reading, Gillwise pre-fills the current value from your latest test and sets a sensible default target for your tank type. You can change any value before calculating.
The CSV has empty cells — is something missing?
Empty cells mean you didn't log that parameter in a given test. Gillwise only records what you actually enter, so partial tests are normal and valid.
Is the Fish Health Guide a substitute for veterinary advice?
No. The guide is general hobbyist reference information, not veterinary care. Fish diseases can be hard to distinguish, and water quality is the most common root cause — always test your water before medicating. Consult a specialist for serious or persistent illness.
Where is my data stored?
Tank data is saved to a JSON file in Application Support on your device. Settings are stored in UserDefaults. Nothing is uploaded or backed up to a server.
How do I delete a tank or reading?
For tanks: open the tank, tap ··· at the top right, and choose "Delete tank." For readings: swipe left on a reading row in the Water tab, or open the reading and tap the trash icon.