Does the water in your sump separate/fractionate by salinity?

[Joe31415]

I'm sure we've all seen what happens when our ATO kicks on and the RODI water mixes in with the salt water. You can see the RODI water in the sump. It almost has that 'mirage' look that comes off the asphalt on really hot days.

What I never really noticed until recently was that in the return section, which is where the ATO fills, the RODI sits up on top. The other day, I had kicked up some of the debris in that section so it would find it's way, through the DT, back to the filters, but when I did it, I noticed all the RODI started swirling around and make it's way through the DT as well.

I doubt it's a huge deal, but I never really noticed it before. I always figured that even though it floated on top, it would eventually mix itself back in. If for no other reason, eventually they're be so much RODI, it would meet the pump intake.

I'm going to move my RODI line to right in front of the pump intake so as much as possible gets moved into the tank immediately.

I don't recall seeing anyone ask about or mention this before. I doubt I'm the only one that's noticed this.

 

[MnFish1]

I'm sure we've all seen what happens when our ATO kicks on and the RODI water mixes in with the salt water. You can see the RODI water in the sump. It almost has that 'mirage' look that comes off the asphalt on really hot days.

What I never really noticed until recently was that in the return section, which is where the ATO fills, the RODI sits up on top. The other day, I had kicked up some of the debris in that section so it would find it's way, through the DT, back to the filters, but when I did it, I noticed all the RODI started swirling around and make it's way through the DT as well.

I doubt it's a huge deal, but I never really noticed it before. I always figured that even though it floated on top, it would eventually mix itself back in. If for no other reason, eventually they're be so much RODI, it would meet the pump intake.

I'm going to move my RODI line to right in front of the pump intake so as much as possible gets moved into the tank immediately.

I don't recall seeing anyone ask about or mention this before. I doubt I'm the only one that's noticed this.

I agree the way to 'fix' that is more flow as you planned. Clearly there are areas where detritus accumulates - where the flow is lower - so what you say makes sense.

 

[Karen00]

Now I know what that mirage look is. This is my first SW tank and it's bare bones (no sump, etc) so my freshwater goes straight into my dt. I have noticed this mirage look when adding the freshwater. I wasn't sure if I was doing something wrong and meant to research it but now I know what's going on so I don't have to. I'm glad I read this.

 

[Joe31415]

Now I know what that mirage look is. This is my first SW tank and it's bare bones (no sump, etc) so my freshwater goes straight into my dt. I have noticed this mirage look when adding the freshwater. I wasn't sure if I was doing something wrong and meant to research it but now I know what's going on so I don't have to. I'm glad I read this.

Yeah, that's normal, it just caught me off guard when my return nozzle filled the tank with swirling RODI. It cleared up in a few minutes, I just wasn't expecting it. Like I said, I assumed that even if it floated on top, it eventually mixed itself in.

 

[MnFish1]

Yeah, that's normal, it just caught me off guard when my return nozzle filled the tank with swirling RODI. It cleared up in a few minutes, I just wasn't expecting it. Like I said, I assumed that even if it floated on top, it eventually mixed itself in.

PS - my guess is that unless that area in your sump keeps getting deeper and deeper - it is eventually mixing in for the most part.

 

[Karen00]

Yeah, that's normal, it just caught me off guard when my return nozzle filled the tank with swirling RODI. It cleared up in a few minutes, I just wasn't expecting it. Like I said, I assumed that even if it floated on top, it eventually mixed itself in.

I've always noticed mine mix in quite quickly which is probably why I kept forgetting to research it. I'm assuming it's mixing fast enough because I have never had any issues like a fish suddenly dying in a swell of freshwater or weird parameter changes although I don't have real time monitoring like an Apex. I just usually check the salinity after adding my freshwater and that always stays stable.