how the auto water changer works!

atu-pro4 - 30 litre

atu-pro4 - 30 litre

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Auto Top Up (not water changer)

ATU-Pro4 - 30 litre fitted with capacitive sensor

  • Dimensions: D:350mm W:270mm H:370mm (height does not include the cap - 420mm total)

  • Large 8" opening lid
  • sensor and controller are mounted on the aquarium or sump, provided with 3m pump power feed extension 

This unit has been designed to be plug and play

includes pump/pipe/mounting etc 

shipping £12.50 uk mainland


Here are a few scenario's that have been reported on reef sites and what the ATU-PRO3 does if it happens.

  • The float physically jams because of a snail or similar
  • The float fails electrically
  • The float drops into the tank
  • The outlet comes adrift resulting in water outside the tank
  • The reservoir runs dry (possible pump burn out}
  • The pump gets jammed
  • and most important R.O. reservoir "dumps" its contents into the aquarium

In every situation above only the ATU-Pro3 will shut the pump down after a time period set by yourself with the options of 5, 10, 20 or 60 seconds. - exclusive to Reefloat - NO other brand has this facility

The ATU-PRO3 is pre-wired and the unit is ready to use - includes:

  • The programmable controller
  • Supplied with infrared sensor and magmount
  • A low voltage pump with a maximum height of 2 metres
  • A 2amp power supply
  • 2 metres pipe
  • 3m extension cable for pump
  • full installation guide



In a nutshell it shuts down the pump so the top-up is inoperative until you come along and reset it, indication that it has shut down is via the pump LED starts flashing and the alarm sounds for 30 seconds, sounder then repeats for 2 seconds at 15 minute intervals. Reset is a simple push of the button, once to silence the alarm and twice to full reset - if the cause of the fault is still present then it will go back into alarm state


BONUS - Anti-Wave - many are familiar with the pump switching on and off every time you stick your hands in the water, or the same things happens if you have that powerful wave maker powerhead. This is addressed by a 3 second built in float delay activation, in other words the water level has to be "LOW" for 3 seconds before the pump starts, as soon as the level reaches a "HIGH" position the pump stops immediately. The distance between high and low level is not measurable by conventional means the sensor is that accurate!

BONUS - Memory - that preset time you set up stays unless you reprogam, it is not lost on power failure!


  • sensor - capacitive
  • sensor cable length 40cm (designed to be positioned alongside the controller-we do not advise extending the cable length)
  • water level variance - less than 0.5mm
  • voltage - 12v DC
  • alarm - visual and audible programmable 5-60 seconds, pump auto cut-off on alarm
  • pump - 12v DC with up to 3m head height 
  • anti-wave - 3 second delay on pump activation
  • sensor mount - custom (exclusive)

    Customer Reviews

    Based on 5 reviews Write a review

    Customer Reviews

    Based on 1 review
    Ryan Dawson (Rossendale, GB)
    Fantastic Product

    This ATO is essential, I have full confidence now the system is being topped up whenever it is needed. The failsafes provide me with comfort in knowing the device will handle things effectively and I will be notified to resolve any issue without a flood. The device knows when my hands are in the sump and won't trigger, another great feature. Overall I highly recommend to anyone.