how the auto water changer works!

auto topup kit - pro4 programmable
auto topup kit - pro4 programmable

auto topup kit - pro4 programmable

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NOTE: the version 4 now incorporates an updated sensor which is slightly larger than the original shown in the video, there are no difference's other than physical size!


  • sensor cable length 40cm (designed to be positioned alongside the controller-we do not advise extending the cable length)

suitable up to 9mm glass/acrylic, clear or not clear

overseas shipping available

The ATU-PRO4 has all the same safety features of the ATU-PRO3 - the difference is in the sensor type, its outside the aquarium not in!

2 year sensor guarantee!

ATU4 is pre-wired and the unit is ready to use - includes:

  • The programmable controller
  • Supplied with sensor and mount
  • pump
  • A 2amp power supply
  • 2 metres small bore pipe w/hook outlet
  • full installation guide online


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. 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 3 reviews Write a review

    Customer Reviews

    Based on 27 reviews
    Melody Carrier (Beaumont, US)
    Great Products

    I originally order the AWC which is great. No more buckets and it works great. I then got the ATU, it is wonderful also. No more daily top off. Love these products.

    Terry Greene (South Ockendon, GB)

    This atu is great so easy to install soon as I have the money I will be back for the water change unit 👍

    kevin boniface (Haywards Heath, GB)
    Pro 4

    Good product and very helpful when I had a o

    Jim Adams (Manchester, GB)
    Great service

    Had some problems setting up (not a fault with design) and contacted Gordon. He called back and talked me through solution. Because of my setup we couldn’t access where I needed to. No problem- Gordon sent me a different sensor and now it’s all working.
    Excellent service.
    Thank you Gordon.

    Steven Webb (Halifax, GB)
    Auto top up kit pro4

    So far this is great piece of kit. No sensor in the tank to get dirty or salt encrusted.
    I found it difficult to place the control box as I use it on an AIO nano and the cable from the sensor to the control box is very short.
    It would be handy to have a line or mark on the sensor to show where it senses the water level but other than that it's perfect, very pleased.