ATO overfilling.

[ourfirsttank]

The levels in the rear sections of the tank have recently dropped below where they were. This is causing the ATO to fill even though the levels in the main tank are normal. What can be causing this?

 

[Quietman]

I assume your tank is an AIO style with the equipment in a compartment in the rear of the tank and no sump.

Where is your level sensor located?

 

[ourfirsttank]

I assume your tank is an AIO style with the equipment in a compartment in the rear of the tank and no sump.

Where is your level sensor located?

It’s a 15 gallon hello reef cube. Here is the set up

 

[Quietman]

It looks like the ATO sensor in the return section (not familiar with your specific tank). That's the section with the pump in it. As it should be. In normal operation the return section will be only one affected by evaporation (as least until it's empty). The main tank level will always be stable at the height of the weir (overflow).

If your ATO is not in the return section with the pump you could have more level fluctuations in the rear compartments.

 

[ourfirsttank]

It looks like the ATO sensor in the return section (not familiar with your specific tank). That's the section with the pump in it. As it should be. In normal operation the return section will be only one affected by evaporation (as least until it's empty). The main tank level will always be stable at the height of the weir (overflow).

If you're ATO is not in the return section with the pump you could have more level fluctuations in the rear compartments.

You are correct - the ATO is in the same chamber as the return pump. It was working fine for 3 months until yesterday after we cleaned the sponge. When the pump is turned off, the levels return to normal and level across all chambers.

 

[Quietman]

If your pump is turning on and filling to the sensor height in the return section, then the ATO is working.

A clogged sponge may impact level depending on location but usually it only means that it'll overflow the section divider.

If the level in the rear section is high enough for equipment to operate and is stable, I would go with it being a new normal.

 

[Quietman]

Thinking a bit more, you could have a leak between the dividers. That would cause the adjacent sections to be at the same level as the return section. Seems unlikely but it's worth considering if the above doesn't match what you're seeing.

The easy fix would be to raise the ATO sensor.

 

[Quietman]

Looking at your pic again, is the ATO supply under the water? If so, you could easily have a reverse siphon drawing water out of your tank into ATO reservoir. Sorry didn't see that before.

You always want an air gap between the ATO supply and your return section water level even when it's at the highest level when the return pump is off. This prevents a siphon drawing water out.

 

[Amstar]

Is your inlet /weir blocked by anything (algae/sponge not down as far as it was) -

Usually I find on my 15 gallon AIO if the main tank is higher and the return is low causing the ATO to run its with the inlet /weir not letting water in

 

[ourfirsttank]

Looking at your pic again, is the ATO supply under the water? If so, you could easily have a reverse siphon drawing water out of your tank into ATO reservoir. Sorry didn't see that before.

You always want an air gap between the ATO supply and your return section water level even when it's at the highest level when the return pump is off. This prevents a siphon drawing water out.

That was it! Thank you so much! The tube must have moved when the sponge was put back in. Thanks again!