SentinelTelegrahamTested
Accessible aquarium projects

Your aquarium.
Your equipment.
Your control.

Budget-friendly ideas for complicated aquarium challenges. Explore familiar electronics, learn by doing, and get more from the equipment you already own.

Explore the projects Meet the builder

Approachable projects. Established technology. A no-subscription philosophy.

PRACTICAL PROJECTS. ONE REEF.Sentinel AlarmSentinel FlowSentinel LinkSentinel FlashSee every active alarm.Pumps working together.Explore equipment connections.Wireless GHL firmware updates.Apex → chosen notifications10 reefs · tides & weatherLights & pumps · MobiusWi-Fi → ESP32 → USBBETAIN DEVELOPMENTEXPLORATORYBETAMORE FROM THE EQUIPMENT YOU OWNSentinel VaultLocal HYDROS control.Outlets · alerts · bus healthCOMPLETE & FUNCTIONING · PRIVATEAffordable partsLearn by doingNo-subscription philosophy
01 Approachable at every level
02 Budget-friendly by intent
03 Established building blocks
04 Local-first, no subscription
The Sentinel projects

Complicated challenges.
Practical starting points.

Explore six independent projects, from open learning to restricted research, working toward more affordable aquarium technology. Each project is clear about what is ready and what is still being explored.

S / 06Phone or computerSimple browser interfaceLocal Wi-FiSentinel FlashESP32 USB bridgeUSBYour GHL deviceCONNECTION OVERVIEW · DEVICE COMPATIBILITY VARIES
Beta

Sentinel Flash

An ESP32 connected to your GHL device’s USB port makes device firmware updates wireless, with a simple browser interface on your phone or computer.

Explore Sentinel Flash Register beta interest ↗
S / 01SENTINEL ALARMWATCHINGAPEX ALARM CONDITIONSTemperature highpH lowReturn pump alarmACTIVE9:41Notifications3 active alarm conditionsSENTINEL · nowTemperature high!SENTINEL · nowpH low!SENTINEL · nowReturn pump alarmEXAMPLE ALARMS & APP · USER-SUPPLIED HARDWARE
Beta

Sentinel Alarm

Sentinel Alarm watches your Neptune Systems Apex for alarm conditions and notifies you through your chosen notification provider. It’s also a hands-on aquarium project built around simple, inexpensive electronics—with plenty of room to discover and learn.

Explore Sentinel Alarm Join the waitlist
S / 0210 REEF LOCATIONS12345678910NATURAL TIDAL CYCLESWEATHER & WATERCOORDINATED FLOWYOUR LOCALTIMINGCONCEPTUAL LOCATIONS & PATTERNS · NOT MEASURED DATA
In development

Sentinel Flow

Sentinel Flow brings flow pumps from different brands together and coordinates them to mimic natural water patterns. It uses real data from 10 reef locations, with timing adjusted to your location—bringing a little more of the reef’s rhythm into your aquarium.

Explore Sentinel Flow
S / 03CONNECTED POSSIBILITIESBLUETOOTH HUBLIGHT 01LIGHT 02PUMP 01PUMP 02HUB TO DEVICESDEVICE TO DEVICECONCEPTUAL CONNECTIONS · DEVICE SUPPORT UNVERIFIED
Exploratory

Sentinel Link

Exploring practical, budget-minded connections involving EcoTech Marine’s Mobius platform. The goal is useful integration with understandable technology; capabilities still need testing.

Explore Sentinel Link
S / 04LOCAL HYDROS CONTROLRESTRICTEDController onlineData freshness · currentAQUARIUM TEMPERATURE78.1°F0 alertsOUTLET CONTROLOutlet 01ONOutlet 02AUTOBUS POWER HEALTHVOLTAGECURRENT24.2 V180 mAController temperature32°CSelf-testPASSILLUSTRATIVE VALUES · METHOD WITHHELD · NO PUBLIC RELEASE
Complete and functioning

Sentinel Vault

Complete and functioning: local HYDROS monitoring and control, from aquarium temperature and outlet states to controller and bus power health. The implementation stays private.

Explore Sentinel Vault
S / 05APEX + GHLOne shared viewALARMSHOME ASSISTANTONE DESKTOP. A CLEARER VISION.
Complete and functioning

Sentinel for Mac

A completed personal Mac app, not available for others to use, that brings Apex and GHL equipment—including devices without supported APIs—into one view. Stronger alarming and Home Assistant integration make that information more useful, helping you understand what needs attention.

Explore Sentinel for Mac
The fun bucket

There’s more in the craft room.

GHL access, distributed aquarium control, solar, home automation and small experiments with room to grow.

See what I’m playing with
The philosophy

More possibilities.
Less expense.

Useful technology should be within reach. Sentinel starts with familiar, well-documented building blocks and looks for budget-friendly approaches to problems that can feel complicated or expensive.

The story behind Sentinel ↗
  1. 01
    Make the first step approachable.

    Plain explanations, small experiments and room to learn. Bring your curiosity, whether this is your first electronics project or your next deep dive.

  2. 02
    Make the budget count.

    Explore what inexpensive, readily available electronics can do before reaching for another costly solution. A local-first direction and no-subscription philosophy guide the work; actual parts costs and release terms remain to be defined.

  3. 03
    Use proven foundations. Test the rest.

    Established components and documented tools provide a starting point. Each Sentinel project still needs its own testing; familiar technology does not automatically establish compatibility or reliability.

Before you dive in

A few useful answers.

Can I download or buy a Sentinel product today?

No release files, pricing or purchase options are published here. Sentinel Alarm has a waitlist; Sentinel Flash is in beta with interest registration open; Sentinel Flow is in development, and Sentinel Link is exploratory. Sentinel Vault’s local HYDROS monitoring and control is complete and functioning in my personal setup; its implementation remains private. Sentinel for Mac is complete and functioning in my own setup, with aggregation, alarming and Home Assistant integration. See project status for the current scope.

Does local-first mean everything is offline?

No. It describes the project direction, not a verified capability across all projects. These websites are hosted online, and contact or waitlist submissions use an email service.

Are these manufacturer-supported products?

No. Sentinel is independently hobbyist-built and is not affiliated with the equipment manufacturers.

Curious about what’s next?

Follow Sentinel Alarm or Sentinel Flash development, share equipment details, or start a conversation.

Let’s talk