Water parameters different in sump to display

[Daniel225]

been testing no3 weekly past month and seems to be 0ppm in sump where i test i thought to myself yesterday I’ll test sump and display at the same time and the display came back at 5ppm and the sump 0ppm

is this normal can’t find anything online related other than a old thread from 2015 and didn't really explain anything for me

 

[Someshmuk]

You have water in the display that isn't making it into the sump or it isn't mixing well enough with the water coming from the return before it heads back to the sump. Check the flow pattern in your display and adjust accordingly or invest in a powerhead.

 

[mtraylor]

Herbie style overflow?

 

[Someshmuk]

Herbie style overflow?

Specifically I'm talking about how the flow is going through your display. Your return outlets could be sending water directly into your overflow for example. It's probably only circulating a part of your tank and the rest is still sitting in the display.

 

[mtraylor]

I'm not the OP and do not have this problem. The question about Herbie style overflow is for the OP.