See every active alarm—not just the first notification. Sentinel Alarm independently watches your Neptune Systems Apex for alarm conditions and sends notifications through your chosen provider, even while another alarm is still active. Free software, simple electronics you supply, and room to learn as you go.
Formerly Apex Sentinel. This is the public project and waitlist site. Private beta 1.9.2 is available to eligible testers ↗; the general release is still pending. Explore the project story ↗
Leave your email and I'll let you know when Sentinel Alarm is ready to download. No purchase or payment required to join.
Your email will be used only for Sentinel Alarm release updates. This form does not place a hardware order.
The current private beta includes builds for ESP32 development boards, M5Stack Core2, and the original LILYGO T-Display. You supply the hardware; Sentinel Alarm software is free; the general release is pending.
A compatible development board with at least 4 MB of flash, a data-capable USB cable, and a USB power supply, plus 2.4 GHz WiFi and a reachable Neptune Apex controller, are needed to get started.
Set up WiFi, Apex connections, and notifications in your browser. Add an optional buzzer or relay if you want a local audible alarm.
See an ESP32 hardware option ↗If you decide to move up to the Core2, these features improve your Sentinel Alarm experience.
Supported Core2 revisions: V1.0 and V1.1/V1.3. Select the Core2 build in the installer.
To detect tank power loss, plug the Core2’s USB supply into the same circuit as the tank. Remote power-cut notifications still need a working network; a UPS for your router and modem can keep that path available.
View M5Stack Core2 on Amazon ↗The original ESP32 model with a 1.14-inch, 240 × 135 color screen and 4 or 16 MB flash has its own beta build.
No built-in speaker or vibration, and no Core2-style USB power-cut detection. T-Display-S3 is a different model; this display build is for the original ESP32 board.
Sentinel reads the Apex’s local status API and monitors up to four controllers. Watch readings, leak/float switches, outlet power, and output states. It does not change Apex settings or control equipment. Local API compatibility depends on your Apex firmware and network setup.
Install by USB using Chrome or Edge on a computer. Configure WiFi, Apex connections, and alarms in the browser walkthrough. After setup, Sentinel runs on its board; a computer does not need to stay on for alarm monitoring.
The private beta includes a read-only live view. Tailscale remote access needs a separate always-on home device, such as Home Assistant, a Raspberry Pi, or a PC. Use a reserved device IP and your actual home subnet. Never port-forward Sentinel. Alerts work without Tailscale.
Choose Pushover, ntfy, Telegram, Discord, Slack, Gotify, a webhook, MQTT/Home Assistant, or a local buzzer/relay. Third-party services may require an account or have fees. Sentinel shows current readings, with no long-term graphs or history. Keep your existing aquarium protections and test the whole alert path.
Here’s how you’ll get started when the software is released.
Connect it by USB, then open the browser-based installer in Chrome or Edge on a computer. The installer detects the chip; for a classic ESP32, choose generic ESP32, M5Stack Core2, or original T-Display. A first installation erases the board.
Restart the board, join its ApexSentinel-xxxx setup network, and follow the browser walkthrough to connect to your home WiFi and find your Apex.
Set your alarm conditions and notification channels. Send a test notification and safely test an alarm so you know the whole path works.