Strips or API master kit readings? Which one should I trust.

[DLMyth]

So curious which one should I trust. Co-op strips shows 6.8 but could be 7.2 PH. But master kit shows 7.6-7.8 PH

[Sarina]

Well judging by your Kh, your pH should be around 7.2-7.6. It's always a little difficult to tell in photos, but the test strip kit needs to be done in a very specific way for accuracy. Unless you took the photo at 1 minute, as the instructions state, the reading may be off. I recommend retesting with both if the ph number is crucial. If it's not that important, I wouldn't worry too much about it. Swings of 0.2 in either direction from the average aren't really anything to worry about unless you're keeping the most sensitive of wild caught species. 

[Fish Folk]

In both cases, colors are hard to pinpoint with precision. Even the API titration tests have a certain shelf life... may require special shaking in reagents... etc.

My view is this: as long as your parameters aren’t majorly out of sync with keeping fish healthy, you’re fine.

I tend to trust the API drops. But I also think of it like... the differences in “time” between my cheap battery powered watch, the clock on my used car, my wife’s alarm clock in the bedroom, and my iPhone. They’re all different... but fairly close. Plus, I tend to go by _one_ or _another_ not by all four at the same time.

So, in other words, choose one and stick by it. Measure variance by strips vs strips, or drops vs drops — not so much against each other.

If this drives you nuts, you can spend about $350 for a digital meter.

[Daniel]

I agree with @Fish Folk. I like the convenience of the strips. And if I need a more precise answer I have the lab equipment I need.

[The Goatee]

Determining color gradients are hard on these tests. Even the vials are hard to distinguish between adjacent levels for me. The light source you use can also make colors look different. Those strips will warp results if you dip too long or read them too early / late. I think the drops and vials are more accurate overall though, I’ve never seen major deviation in results when following instructions. Only one color grade different maybe.

I really only use any test kit when first setting up to monitor ammonia and nitrite. I may test once a week or month to verify nothing weird is going on and that everything looks consistent to past tests. I think people have said making sure things are consistent is more important than trying to achieve something specific in most cases, unless it is a very specific parameter and more advanced fish/stock.

[tonyjuliano]

On 6/22/2021 at 2:48 PM, Fish Folk said:

If this drives you nuts, you can spend about $350 for a digital meter.

There are plenty of digital pH testers out there that cost under $30.  The key to getting a reliable one is if it’s calibrate-able (not all are) and also has auto temperature compensation (again, not all do).

I do liquid testing on Sundays, when time for my other maintenance is also planned, but mid-week I use strips that I’ve found to be reliable and repeatable.  I also rely on strips for daily monitoring of cycle progression in new tanks.

And as far as strips for ammonia testing go, I’ve only found a few brands that I trust.  In my experience, if the ammonia test strips  don’t come packaged with desiccant and/or a special cap to absorb moisture, I won’t use them.