ATO - what chamber for fill

[Uncle99]

Hi Everyone:
When employing an ATO in a sump, does it matter which chamber, 1st, 2nd, or return, the ATO fills?
I Have it filling the return chamber but seem to get a lower salinity over a few days by say .001, as if the ATO adds a bit more than it should. It seems to turn on/off, never triggers the safety stop.

This ATO works perfectly when used in a DT with no sump. Always kept SG, butt on.

Can you help, is there something in sump application ATO which might account for this?

I would appreciate anything you can share.

180g mixed, 40g sump 12’ feet below in fish room.
3 chamber sump with Jebao DCQ 10000.

 

[Biglew11]

It doesn't really matter were the ato fills the sump. But what does matter is were the ato sensors are located. Those should be in the return section. Or the section of the sump that's the lowest level while everything is running.

 

[Biglew11]

Are you skimming very wet? This will remove alot of saltwater that can slowly cause your ato to decrease salinity by replacing saltwater with rodi. Depending on how wet I skim I'll replace the skimate with new saltwater.

 

[GaryE]

I fill between the refugium and return. It's a baffle area with a sponge.

 

[Uncle99]

Thanks for those responses.

I have both the sensor and fill in the return, not much skimate yet. The tank is an upgrade and has 4+ year old rock and corals, chaeto, and two marine pure rocks in the sump180g but only 6 3” fish, so low load.

I put it back to 1.026, I will watch carefully and see what happens.

At least I know I’m set up like you guys out there, so either I’m dreaming, the refractometer is wrong, or the sensor is malfunctioning......

 

[Uncle99]

Are you skimming very wet? This will remove alot of saltwater that can slowly cause your ato to decrease salinity by replacing saltwater with rodi. Depending on how wet I skim I'll replace the skimate with new saltwater.

Looks wet to me, not a ton of DOC, but cup has a hose attached directly to waste.
I have plugged that hose for now to see what volumes might be.
Good thinking