David S
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- Jul 23, 2016
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OK, so last week it was time to change my GFO. I know from experience that unless you wash the GFO carefully before putting it in your system it could lead to a precipitous drop in the tank's PH.
So I carefully rinsed the Rowaphos until I could no longer see any discoloration in the water that was coming out of my HOB reactor.
I then placed it on my tank about mid afternoon. From that point until the following morning when I was to test my Alkalinity, I noticed that the PH had dropped. Certainly not much to be an issue, but I was surprised, as I thought I did a thorough job of washing the GFO.
I then tested my Alkalinity, using my Salifert kit.
My result indicated a DKH of barely 7.0. A bit low for my system which had been consistently in the 7.5 to 8.5 range the last two months.
Decided to compare this result with the Hanna Alk checker.
As mentioned in a previous thread when comparing Salifert vs Hanna, depending on how I interpret the color change of the Salifert test, the results between the 2 tests could be spot on, but have no more than a 0.4 difference.
Had to do some head scratching when I got a result of 8.8.
I retested both an additional two times. In the Salifert, I did my 3rd test with a newer reagent, although both reagents were well within their expiration dates. All 3 results were the same, about 7.0.
In the case of the Hanna, the 2nd test was 8.7. I decided to do a 3rd test with the other testing cuvette provided, and it came out to 8.6.
Since I had a Red Sea Alkalinity test kit, as well, I decided to test with that. My first result indicated a DKH above 9. However, as it is difficult to interpret the "right" color change for this test -which is the reason I rarely use it- I performed a 2nd test which fell into line with the Hanna results.
In spite of the "consensus" of the Hanna and Red Sea tests, I could not accept the inaccuracy of the Salifert test, as I've used it for years with no issues.
My guess is this had something to do with the GFO switch out I did the day before. I could think of nothing else that may have caused it.
The question being; is it a general issue with GFO or is it more brand specific. In this case Rowaphos.
Also wondered which if any of the tests may have been accurate.
Of course it's possible they were all distorted but I suspect it is the Salifert that was more accurate since there was also a definite - though not dramatic - drop in PH after changing the GFO.
Finally, I should point out that within 2 days all 3 test kits normalized and were all giving similar results.
I'd like to know if other people have experienced this. If so what may cause it.
I will monitor, closely, next time I replace my GFO
So I carefully rinsed the Rowaphos until I could no longer see any discoloration in the water that was coming out of my HOB reactor.
I then placed it on my tank about mid afternoon. From that point until the following morning when I was to test my Alkalinity, I noticed that the PH had dropped. Certainly not much to be an issue, but I was surprised, as I thought I did a thorough job of washing the GFO.
I then tested my Alkalinity, using my Salifert kit.
My result indicated a DKH of barely 7.0. A bit low for my system which had been consistently in the 7.5 to 8.5 range the last two months.
Decided to compare this result with the Hanna Alk checker.
As mentioned in a previous thread when comparing Salifert vs Hanna, depending on how I interpret the color change of the Salifert test, the results between the 2 tests could be spot on, but have no more than a 0.4 difference.
Had to do some head scratching when I got a result of 8.8.
I retested both an additional two times. In the Salifert, I did my 3rd test with a newer reagent, although both reagents were well within their expiration dates. All 3 results were the same, about 7.0.
In the case of the Hanna, the 2nd test was 8.7. I decided to do a 3rd test with the other testing cuvette provided, and it came out to 8.6.
Since I had a Red Sea Alkalinity test kit, as well, I decided to test with that. My first result indicated a DKH above 9. However, as it is difficult to interpret the "right" color change for this test -which is the reason I rarely use it- I performed a 2nd test which fell into line with the Hanna results.
In spite of the "consensus" of the Hanna and Red Sea tests, I could not accept the inaccuracy of the Salifert test, as I've used it for years with no issues.
My guess is this had something to do with the GFO switch out I did the day before. I could think of nothing else that may have caused it.
The question being; is it a general issue with GFO or is it more brand specific. In this case Rowaphos.
Also wondered which if any of the tests may have been accurate.
Of course it's possible they were all distorted but I suspect it is the Salifert that was more accurate since there was also a definite - though not dramatic - drop in PH after changing the GFO.
Finally, I should point out that within 2 days all 3 test kits normalized and were all giving similar results.
I'd like to know if other people have experienced this. If so what may cause it.
I will monitor, closely, next time I replace my GFO
