Not sure which pH reading to trust

flmlly

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I've had my tank set up since October 10, 2020. It has a 90 gallon display, and about a 100 gallon sump setup in the basement with live rock, a refugium, and a deep sand bed. I have 12 very small fish in it, and two bubble tip anemones. Everything seems to be thriving, and despite having slightly high Nitrates and Phosphates, the chemistry seems to be mostly under control and consistent. My problem has been pH, or at least, figuring out what my pH is. I have had a Seneye on the system from the start saying the pH floats around 7.6-7.8. I recently purchased a Hanna Instruments HI780 pH checker that from it's first use just flashes 8.6, indicating the water is above 8.6 and out of range. I purchased the Hanna pH certified standard kit to test my new colorimeter, and acceptable readings per the standard were 7.9 to 8.1. Mine read 7.8. I returned the original colorimeter since it was out of range and purchased another one, but it read 7.8 as well when testing the certified standard. So either the standard is inaccurate, which seems unlikely since it comes with a certificate of analysis, or both my meters are wrong and reading low, not high. I have to trim my Seneye a full 1.0 up to match the pH reading from the Hanna checker, which seems like a lot to me.

My question is should I trust the 8.6+ reading I've gotten from two different Hanna checkers? If so, I am not sure how to lower my pH. I've dosed vinegar in small amounts, but get cloudy water, and the lowering effects are only temporary. I've stopped running the protein skimmer intake outside, I've shortened the duration of the refugium lights to 6 hrs/night, stopped using soda ash to control alkalinity, and I've lowered my alkalinity to 9. It doesn't seem like a normal problem to have pH this high. My goal is to keep it around 8.2-8.3 since that seems to be what most people suggest, but don't want to do anything drastic to get there since everything in the tank seems to be doing well.

It's important to note that when I've dosed vinegar to lower pH, the Hanna checker is recognizing the drop.

Lately I've been wondering, if the pH reading of 8.6+ is, in fact, accurate, that maybe the very small amount of fish I have relative to the volume of the water could have something to do with it. Is it possible there aren't enough fish producing CO in the aquarium to lower pH naturally? Other than a 4" long goby, none of the fish I have are larger than 2". I have a fairly large house, and a family of 3 that isn't home most of the day, so maybe there isn't enough CO in the house to lower the pH? I'm out of ideas at this point.

Thank you.
 
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Uncle99

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I would not overthink the PH in terms of test kits, as you can see, who can you trust.
I trust the 7.8 way before the 8.6 cause the later doesn’t make sense.
Many ways to increase PH, my list is.
Dose Alk only when lights off.
Blow fan across the water surface
Dose Carbon only when lights on.
Bring in outside air to skimmer.
 

Billdogg

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^^^What Uncle99 said^^^

I haven't checked pH in probably 30 years. It is so dependent on various environmental factors that it's just a waste of time, effort, and $$$.

You really want to drive yourself nuts? Check it first thing in the morning, about an hour after lights come on, right before lights out, and then an hour or two later. They will all have different results. Summer vs Winter, have a party with a bunch of people over, etc etc etc.

As long as the Calcium, Alkalinity, and Magnesium are in range and steady, Nitrates and Phosphates are at acceptable low levels, and there is no real level of Ammonia or Nitrite, your tank is doing just fine. Chasing a specific pH will just throw the big 3 all out of wack, and that will bring a whole other list of problems.

JM.02
 
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