how the auto water changer works!

atu3-programmable 30 litre
atu3-programmable 30 litre
atu3-programmable 30 litre
atu3-programmable 30 litre
atu3-programmable 30 litre

atu3-programmable 30 litre

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Auto Top Up (not water changer)

ATU-Pro3 - 30 litre fitted with an infrared sensor

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

  • Large 8" opening lid

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 with 2m flex
  • A low voltage pump with a maximum height of 3 metres
  • A 2amp power supply
  • 2 metres pipe
  • 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 - HQ infrared
  • sensor cable length 2 metres
  • sensor mounting -magmount
  • pipe - 5mm internal, 2m supplied 
  • 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

Customer Reviews

Based on 5 reviews Write a review

Customer Reviews

Based on 5 reviews
Tidy Atu and great service

Am new to reefing but knew I had to get an Atu.

Reefloat kept getting mentioned and I'm glad I took the plunge.

Unit is well made and fits nicely in the reefer 250.

Had some issues due to an accident and Gordon's support was ace.

so, I ordered the AWC too

Matthew Miller
Simply awesome

This unit has saved me so much hassle compared to my old red sea reservoir. It'll last me a good two weeks, the container nice and strong and fits snuggled in a separate cabinet.
Gordon kindly fabricated a 30cm sensor as my sump is overly deep and it works spot on.
Hands down the single best purchase in my reefing hobby.

ATU pro3 30 litre

Brilliant system works very well in my sump.
The service from Gordon is second to none. I ordered the standard sensor fitting when I should have ordered the longer version. An email to Gordon and the problem was resolved. He sent an alternative fitting at no charge.
Now that’s customer service

Best purchase

Cannot believe I used to manage with out this.
Great bit of Kit

Dave Cheeseman
Flawless Operation

I replaced the 8 litre top up unit supplied with my Red Sea Reefer with an ATU25 soon after purchase. This gave me greater flexibility as I now only need to fill the unit once a week, and also peace of mind as the sensor is far more reliable than the original float mechanism. The support and guidance given for proper set up and usage of the unit has been invaluable.