ATO: Automatic Top-Off That Won’t Flood Your Living Room

ATO (Auto Top-Off) automatically replaces water evaporated from your aquarium. The mechanism is simple—a level sensor and a pump—but this is where the most costly aquarium failures happen. A stuck float can pump an entire reservoir of RO water into your tank. From day one, Oquari’s top-off system includes built-in safety layers that cannot be accidentally disabled.

Why You Need an ATO

Water evaporates from your aquarium every day—but only pure water leaves. Salt stays behind. Without a top-off system, salinity creeps up day by day, then drops sharply after a water change. For corals and sensitive fish, these fluctuations cause chronic stress. An ATO keeps the water level (and thus salinity) nearly flat by adding small amounts of RO water throughout the day.

How It Works: Float Switch and Pump

The setup is minimal:

• Working float switch – a level sensor placed in the sump or display tank, connected to the designated level input on the Oquari Core controller.
• Top-off pump – a small submersible pump in your RO water reservoir, plugged into the dedicated low-voltage pump output.
• Optionally: solenoid valve and flow meter on the line – Oquari provides clearly labeled connections for both.

The logic is straightforward: if the water level drops and stays low for a set time (brief waves won’t trigger the pump), the controller opens the valve and starts the pump. When the level returns to normal, the pump stops. This entire process runs locally on the controller—it doesn’t need Wi-Fi, cloud services, or Home Assistant to function.

Why Time Limits and Cooldowns Save Your Aquarium

A float switch alone isn’t enough. Common failure scenarios include:

• Float stuck in the down position due to snails, algae, or salt deposits—the pump runs continuously.
• Top-off tube slipped out of the sump—the pump floods the floor while the level sensor never sees a rise.
• Electrically faulty float—the controller reads “low level” indefinitely.

In all three cases, the symptom is the same: the pump runs longer than expected. That’s why Oquari’s top-off function includes multiple independent safety layers:

1. Maximum run time – The controller knows how long a typical top-off cycle should take (e.g., 2 minutes). If the pump runs continuously beyond that, the safety layer forces it off—regardless of what the float switch reports.
2. Daily volume limit – For example, no more than 2% of tank capacity per day. Even a series of “successful” cycles won’t dilute your reef: once the limit is reached, top-off stops and triggers an alarm.
3. Flow confirmation – If you have a flow meter installed, the controller verifies that water is actually moving. A dry pump or blocked tube results in an immediate stop.
4. High-level sensor – An independent float switch placed higher acts as a hard cutoff for overflow, completely separate from normal regulation logic.
5. Lockout after emergency stop – After a safety shutdown, you must manually confirm restart. This prevents the “limit reached → brief pause → pump resumes” cycle that could still flood your tank if the float remains stuck.

These protections override all other rules and schedules. No manual command from the app or automation from Home Assistant can bypass an active safety cutoff.

Set your time limit carefully—and tightly. Measure once with a stopwatch how long a full day’s evaporation takes to top off, then set your maximum run time to 2–3 times that value. A loose limit (e.g., 30 minutes for a tank losing only a cup per day) makes the safety feature meaningless.

Configuration in the Panel

1. Open the controller interface (oquari-XXXX.local) → Water → ATO Top-Off.
2. The wizard will show which components it detected: working float, pump, valve, flow meter.
3. Set maximum run time and daily volume limit (a reasonable starting point is 2% of tank capacity).
4. Save—and test by briefly removing the float from the water: top-off should start, then stop when you return it.

Lockout Alarm

An emergency cutoff does more than shut off the pump—the preset also generates a top-off lockout alarm. You’ll see it on the device and in the web panel, and if you have an oquari.com account or Home Assistant integration, you’ll receive a notification on your phone.

Always treat a lockout alarm as a call to inspect: check the float switch, tubing, and reservoir level before allowing top-off to resume.

After a controller restart, counters reset to zero—this is normal. The time-based protection monitors continuous pump operation, not daily totals, so a brief power loss doesn’t weaken safety in practice: a stuck float will again trigger the maximum run-time limit after the same duration.

Best Practices

• Size your top-off reservoir so that emptying it entirely into your tank wouldn’t cause damage (volume buffer is your last line of defense).
• Clean the float switch during water changes—salt deposits are the most common cause of sticking.
• Add a high-level sensor (Oquari has a dedicated input for this)—it provides an independent, hard cutoff against overflow.
• Install a leak detector under your tank—it costs little and stops top-off before water reaches your floor panels.

Najczęstsze pytania

Does Oquari ATO require internet to work?

No. All top-off logic runs locally on the controller. Internet connectivity is optional and only needed for remote monitoring or Home Assistant integration. Your aquarium stays protected even if Wi-Fi goes down.

What happens if I forget to refill the RO reservoir?

If the reservoir runs empty, the pump will run dry. If you’ve installed a flow meter, the controller detects zero flow and stops the pump immediately. Without a flow meter, the daily volume limit and maximum run time still prevent excessive pumping, but adding a flow sensor is strongly recommended for full protection.

Can I override safety limits manually?

No. Safety cutoffs—maximum run time, daily volume limit, high-level sensor—are absolute. They cannot be overridden by manual commands, schedules, or external automations. This design ensures your tank stays protected even if settings are misconfigured elsewhere.

How do I know if my float switch is stuck?

A lockout alarm indicates a problem. Check for physical obstructions like algae, snails, or salt crust on the float arm. Also verify that the tubing hasn’t slipped out of the sump. Regular cleaning during water changes prevents most issues.

Is Oquari compatible with Home Assistant?

Yes. Oquari integrates natively via MQTT Discovery. Your aquarium appears automatically in Home Assistant as a set of entities—no cloud, no manufacturer account required. You can monitor status, receive alerts, and create automations while keeping all core functions running locally on the device.