Water parameter differences between display and sump

[fixedpoint]

I've always done my tests on display tank water. Today. I was doing something in the sump and decided to take water from there. I thought it's all the same water, but when I ran the tests I got drastically different results. My phosphates were 0.2 ppm, pH was 7.9, alk was 8.5 dKh and so on.

I was concerned and so I grabbed some more, this time from the display tank. The results looked normal again: 0 phosphates, 8.4 pH, alk 10 dKh, ....

Now I'm wondering if others have seen the same thing. I should probably repeat the experiment. My sump doesn't seem to have a lot of flow but clearly the 750 gph return pump is moving water through it.

 

[DamonG]

I've always done my tests on display tank water. Today. I was doing something in the sump and decided to take water from there. I thought it's all the same water, but when I ran the tests I got drastically different results. My phosphates were 0.2 ppm, pH was 7.9, alk was 8.5 dKh and so on.

I was concerned and so I grabbed some more, this time from the display tank. The results looked normal again: 0 phosphates, 8.4 pH, alk 10 dKh, ....

Now I'm wondering if others have seen the same thing. I should probably repeat the experiment. My sump doesn't seem to have a lot of flow but clearly the 750 gph return pump is moving water through it.

That's interesting and following.. Because this current tank,I have the probes in the sump, and I also am showing low ph. But my last tank,I had them in the overflow box of the dt.. I am going to try putting my oh probe in the overflow box to see if there's any difference..

 

[lionfish300]

That is odd I thought both DT and sump should be the same since it the same water

 

[fixedpoint]

It is odd. I'm going to retest tonight with careful attention to make sure I can replicate.

 

[ca1ore]

Cannot explain your results. My sump water tests exactly the same as the display.

 

[disc1]

You have to be doing something wrong. The pH difference I can almost buy since the water in the sump may be better aerated. But the differences in alk have to be due to some testing issue. Like if the water from the sump is stirring really hard and has some little tiny particles of sand or calcium carbonate then that is going to artificially inflate the alkalinity numbers. Sometimes zooplankton can do it too.

 

[ca1ore]

You have to be doing something wrong. The pH difference I can almost buy since the water in the sump may be better aerated.

Yeah, except then you'd expect a higher sump pH, not a lower one.

 

[disc1]

Unless the air it is being aerated with is inside air elevated in CO2 in which case it would be lower.

 

[fixedpoint]

Okay, I carefully retested both the display and the sump. The parameters look identical.

I must have used a contaminated cup when I collected the water from the sump. Or perhaps, I had accidentally included some floating macroalgae that contaminated the sample.

Thanks everyone and sorry for the false alarm. Lesson = be very careful and as consistent as possible when you test.