Large chemistry swing after watered change

[medcinmn]

I’ve been doing the bare minimum on my 34 gal RSM for a while and decided it was time to resurrect it. Initially my chems were phosphates 0.89, nitrates 8.7, Calcium 360 and dKH 12. I did a 5 gallon water change, added calcium over two days and the next test was 490 and dKH 9.6, phosphates .77 and nitrates 7.8. Did another 5 gallon water change 2 days later and retested 24 hours after that. Nitrates 0.7, phosphate 0.79, calcium 380 and dKH 9.
I’m inclined to think I somehow messed up the tests, but fairly certain I didn’t. I’ll retest tomorrow but if they come back the same, any thoughts on these crazy results? Specifically the drop in nitrate and calcium. Salifert calcium and dkh tests, Hanna phosphate and nitrate. I’m using NSW, it tests 0 nitrates, .02 phosphates, 360 calcium and 9 dKH.
I have a Magnesium test kit on the way. All fish and corals (LPS and polyps) look good.

 

[BryanM]

I’ve been doing the bare minimum on my 34 gal RSM for a while and decided it was time to resurrect it. Initially my chems were phosphates 0.89, nitrates 8.7, Calcium 360 and dKH 12. I did a 5 gallon water change, added calcium over two days and the next test was 490 and dKH 9.6, phosphates .77 and nitrates 7.8. Did another 5 gallon water change 2 days later and retested 24 hours after that. Nitrates 0.7, phosphate 0.79, calcium 380 and dKH 9.
I’m inclined to think I somehow messed up the tests, but fairly certain I didn’t. I’ll retest tomorrow but if they come back the same, any thoughts on these crazy results? Specifically the drop in nitrate and calcium. Salifert calcium and dkh tests, Hanna phosphate and nitrate. I’m using NSW, it tests 0 nitrates, .02 phosphates, 360 calcium and 9 dKH.
I have a Magnesium test kit on the way. All fish and corals (LPS and polyps) look good.

Sometimes reagent just doesn’t work right, could be you did nothing wrong.

I always retest when I get a highly abnormal result

 

[medcinmn]

Retested today (did not add anything) and came up with
Nitrate 4.6 Hanna
Phosphate 0.82 Hanna
Magnesium 1280 Salifert
Calcium 460 Salifert
dKH 10.2 Salifert

Guess I somehow may have screwed up. One thing I realized- yesterday I used a medical syringe to draw the water, today I used the Salifert supplied syringes.

 

[Randy Holmes-Farley Verified Community Expert]

Testing is a tricky affair and often folks do not get reproducible readings. Look to trends rather than daily ups and downs. :)

 

[medcinmn]

So I’m an idiot. I took out my media basket to add gfo and found an old bag of Chemipure elite on the bottom rack, broken open. It could be a year old, maybe longer. Sigh. I siphoned out the media from the back chamber and cleaned everything up. Added a few tablespoons of Rowaphos to a media bag and will monitor every couple days.
Incidentally, my nitrates came down even more to 2.1. Will be watching those as well.