Specification
Specification and reliability
Plainly and without marketing: which sensors are supported, how accurately and how often they measure, how you calibrate them, what happens without internet or after a failure, and which features are still in testing.
Supported sensors
| Parameter | Accuracy and notes |
|---|---|
| Water temperature | ±0.5 °C per the sensor manufacturer (−10 to +85 °C), 0.0625 °C resolution. No calibration needed. |
| Room temperature | as above, optional |
| Water level | 1 mm resolution. Ripples and bubbles cause a spread of a few millimetres, so the median of 3 samples is used. |
| pH | depends on the probe; needs two-point calibration because probes drift |
| CO2 | calculated from pH and KH, so it is an estimate: a 0.1 pH error means about 25% CO2 error, and 0.3 pH means twice too high or low |
| Leak | sensor on the floor under the tank: dry / wet, optional |
| TDS | needs calibration with a reference solution, optional |
NO2, NO3, PO4, KH and GH are not measured automatically: you enter drop test results by hand or read a test strip from a photo.
How often it measures
- Every 30 seconds (adjustable in settings), and every 2 seconds during a water change.
- Every temperature and level reading is the median of 3 samples, so one bad sample cannot raise an alarm.
- Invalid values are discarded, e.g. a false 85 °C a temperature sensor can return after a power glitch.
- Full resolution for 30 days; older readings are condensed into hourly averages to spare the SD card.
Calibration
- pH: two-point in the app, in pH 7 and pH 4 buffers. A reminder for the next calibration every 30 days by default.
- CO2: you enter KH from a drop test and update it after water changes.
- Water level: you set the sensor mounting height and the 100% level in the app.
- TDS: a factor from measuring a reference solution.
- Temperature: needs no calibration.
Without internet or Wi-Fi
- Sensors are wired to the Raspberry Pi, so measuring and logging continue without Wi-Fi or internet.
- Alarms show on the dashboard and in the app when your phone is on the same home network.
- Telegram and push notifications need internet. A message that could not be sent is not queued, but an ongoing alarm is repeated every 60 minutes by default (up to 3 times), so the reminder arrives once internet is back.
- Smart plugs are controlled on your home network without the cloud. If home Wi-Fi is down, the plug stays in its last state and the CO2 cut-off cannot switch it off, so treat it as an extra safeguard, not the only one.
When the Raspberry Pi stops working
- Heartbeat: the monitor checks in with an external service (e.g. healthchecks.io). If it goes silent because of a power cut, a failed card or a hang, the alarm comes from that service.
- After an error the app restarts by itself.
- The status panel shows CPU temperature, free space on the card, gaps in data and a sensor that has reported the same value for hours.
- A database backup is made daily (last 14 kept), and optionally sent to Telegram once a week.
- The most common causes of failure are a weak power supply and a cheap SD card: use a 5.1 V / 2.5 A supply and a branded card.
Where your data lives
All readings, tests and photos are stored in the database on your Raspberry Pi. There is no cloud account and no vendor server holding your data. Photos for AI diagnosis go only to a computer on your home network.
What is ready and what is in testing
Until the end of 2026 the whole app is in testing. Within that:
- Stable, used every day: temperature, water level, dashboard alarms, Telegram notifications, history and charts, logbook, water tests, water changes, backups.
- New, in testing: pH probe and CO2 calculation, smart plugs and energy metering, pet-sitter link, maintenance mode, before/after experiment, test strips from photos, leak, TDS and room temperature sensors.
- Experimental, optional: photo diagnosis and AI hints. They need a separate computer running Ollama on your home network, because a Raspberry Pi 3 is too weak. The result is guidance, not a veterinary diagnosis.
What the monitor does not do
- It does not measure nitrate, nitrite or phosphate automatically.
- It does not control the heater or the filter: the plugs are for lights and CO2.
- It does not replace a daily look at your tank.
- It is software on a Raspberry Pi with sensors you connect yourself, not a certified alarm device.
Frequently asked questions
Will the alarm work without internet?
The monitor measures and detects alarms without internet, and you see them on the dashboard and in the app on your home network. A phone notification away from home (Telegram, push) needs internet.
What happens when the Raspberry Pi switches off?
Measurements stop. If you set up a heartbeat (e.g. healthchecks.io), that service tells you the monitor has gone silent. Data up to the failure stays in the database and in the daily backups.
How often should I calibrate the pH probe?
Usually once a month, in pH 7 and pH 4 buffers. The app reminds you every 30 days by default.
Keep an eye on your tank from your phone
The app is free and ad-free. The monitor runs on your Raspberry Pi.