Large daily PO4 swings

[Thales]

last feed was 15 hours prior to this morning’s test, so that rules that out.

I have seen it rise 24 hours after feeding

 

[Ziggy17]

If it were me.. at this point I think I would need to confirm my readings. I would first do at least 3 tests from a single large sample to see if the Hanna gives results all within the correct margin of error. Could it still be a reagent problem? Possibly

I would also be looking at a different test kit to confirm the Hanna results. Or maybe a LFS if they have good equipment to test with.

Hope you figure it out. I don’t really think the tank water is swinging that much in a day all on its own.

Certainly maddening!

I tested it twice back to back and it was within .01 of each other, so unlikely a third was going to read different.

Something is happening for sure and it sure is frustrating.

 

[Ziggy17]

Tested just now and .17 and .14 back to back. Identical procedure.

 

[Ziggy17]

I have seen it rise 24 hours after feeding

What food has ever been known to raise PO4 .8 in 24 hours?