Auto Top Off (ATO) | Water Level LED Refilling | Troubleshooting Bubbles in the Aquarium

Living Oceans

The Auto Top-Off (ATO) system is one of the most important components of your Living Oceans Aquarium. As water naturally evaporates, the ATO automatically replaces the lost water to maintain a stable water level and salinity, helping to create a healthy environment for your fish, corals and beneficial bacteria.

During setup, you'll need to install the ATO sensor, pump and reservoir. Fortunately, the process only takes a few minutes, and once installed, the system operates automatically with very little maintenance.

Watch the video below to see how to install the Auto Top-Off (ATO) system. The guide underneath provides step-by-step installation instructions, startup information and troubleshooting advice.

Why Is the Auto Top-Off (ATO) System Important?

As water evaporates from your aquarium, only fresh water is lost. The salt remains behind, causing salinity to increase if the evaporated water isn't replaced.

The ATO system continuously monitors the water level in the return pump chamber and automatically adds fresh water from the reservoir whenever needed. This keeps the water level and salinity stable without requiring daily manual top-ups.

How to Install the ATO System

Before you begin, ensure the aquarium is switched off.

Step 1: Install the Water Level Sensor

The ATO water level sensor is installed inside the return pump chamber.

  1. Place the green LED water level sensor inside the pump chamber.
  2. Allow it to connect to the factory-positioned alignment magnet on the back of the aquarium.
  3. Feed the sensor cable through to the cabinet.

Step 2: Connect the Power and Pump

Locate the double connector inside the cabinet and connect:

  • The power cable.
  • The ATO pump cable.

Ensure each cable is plugged into its correctly labelled port.

Step 3: Install the Top-Off Hose

Locate the automatic top-off hose and bulkhead fitting.

  1. Unscrew the retaining nut from the bulkhead.
  2. Insert the elbow fitting through the opening in the back of the aquarium.
  3. Refit and tighten the retaining nut.
  4. Feed the hose through into the cabinet.

Step 4: Install the Pump and Reservoir

Connect the hose to the outlet on the ATO pump.

Place the pump on the bottom of the reservoir so it can draw out nearly all of the water during operation.

Fill the reservoir with approximately 15 litres of fresh water. It is recommended to use filtered tap water and tap water conditioner to ensure it is safe. A full reservoir typically provides 4 to 6 weeks of operation, depending on your home's temperature and evaporation rate.

Feed the hose through the opening in the reservoir lid, reconnect it to the pump if required, then slide the reservoir back into the cabinet.

What Happens When You Turn the Power Back On?

After restoring power, you may briefly notice bubbles entering the aquarium. This is completely normal.

When the return pump starts, the water level inside the pump chamber temporarily drops. The ATO sensor detects this change and automatically switches on the ATO pump, adding fresh water until the correct water level has been restored.

Once the pump chamber reaches the correct level, the ATO pump switches off automatically and the bubbles will disappear within a few minutes.

Understanding the ATO Sensor

The LED water level sensor indicates whether the ATO system is operating correctly.

  • Solid green – The water level is correct and the system is operating normally.
  • Flashing green – The ATO pump is actively topping up the water.
  • Red – The system requires resetting.

If the sensor displays a red light:

  1. Turn the aquarium power off.
  2. Wait approximately 3 seconds.
  3. Turn the power back on.

The sensor should reset and return to normal operation.

Routine Maintenance

The Auto Top-Off system requires very little maintenance. To keep it operating reliably, we recommend:

  • Checking the reservoir water level weekly.
  • Refilling the reservoir before it runs completely empty.
  • Confirming the ATO pump remains positioned on the bottom of the reservoir.
  • Inspecting the tubing to ensure it remains securely connected and free from kinks.
  • Keeping the water level sensor clean and free from algae or salt deposits.

Need More Help?

If you've completed the installation steps and the ATO system is still not operating correctly, please contact the Living Oceans Support Team.

To help us diagnose the issue as quickly as possible, please include:

  • Your aquarium model (80L, 130L or 200L).
  • A brief description of the issue.
  • The colour of the ATO sensor light.
  • Photos or a short video showing the ATO reservoir, return pump chamber and sensor.

This information will help us provide the fastest and most accurate support.