Fluval vs API pH Discrepancy

[Rebecca999]

I have been using API pH tests and consistently landing at 7.6 on the low range test and 7.4 on the high range, which I had been assuming put me at 7.5-ish.
Got the Fluval wide range test to try and cover the 'blind spot' between the low and high range results on API but it's vastly different - 6.5!

Any ideas on why the large discrepancy, and which to believe?
I'd be happy to invest in digital if there is a reliable, reasonably priced unit out there and it performs better than liquid tests...

 

[gwand]

That is a huge discrepancy. Did you repeat the test with both kits to rule out operator error. If you get the same result, go for a tie breaker with API dipstick or another kit. I suspect the Fluval kit is off. Decent pH meters are over $100 US. And they need to be calibrated frequently. The cheap kits are not worth it.

 

[JohnnyReb]

That is a huge discrepancy. Did you repeat the test with both kits to rule out operator error. If you get the same result, go for a tie breaker with API dipstick or another kit. I suspect the Fluval kit is off. Decent pH meters are over $100 US. And they need to be calibrated frequently. The cheap kits are not worth it.

Science is not an exact science?

 

[Rebecca999]

Thanks, just repeated both with same discrepancy, and both kits within expiry date.
I then used both on tap water - 6.0 on Fluval and 7.0-7.2 on API. The API best corresponds to the info given by my water supplier so sticking with it for the time being - agreed the Fluval is off, disappointing! Will see if I can get hold of a test strip for a third opinion...