Mixing salt with high PH ro water

[Kpshc707]

Hi all i have some questions about the ph in my reef. i have been testing with a API test kit for my ph and its 8.2-8.4 with that test but i got a Hanna ph meter today and tested it with that and got a reading of 7.8 ph i then tested my saltwater storage barrel and its ph was 7.5 (Coralife salt) then i tested my straight ro/di water and it has a ph of 8.8 then i made up some freth saltwater and its ph was 7.5. My water comes from a creek on my land :headwalls: any ideas? my reef is doing pretty well but have a hard time keeping my alk levels up and my ph according to this meter

[bertoni]

[welcome]

RO/DI water has no buffering, so its pH is unstable. In addition, the meter can't measure the pH accurately due to the low ionic content. So I wouldn't worry about the pH of the RO/DI water.

Salt mixes can mix up to an initial pH that is changes with a few hours of aeration, as carbon dioxide enters or exits the water. I would aerate a container of water outside for a few hours, and measure the pH then. If the alkalinity is between 7 and 11 dKH, the pH should be in the 8.1-8.3 range or so.

How has the meter been calibrated?

[Kpshc707]

Thanks! yeah i read that that too about the DI water. The ph meter is a new Hanna HI 98127 and it was calibrated to ph 7.01 an ph 4.01 i got some mixed water that i have a air stone in outside now. Im also going to pick up some IO reef crystals to test tomorrow. The alk on the new salt water is like 10-11 dkh but the ph is still low i got the ph to 7.9 in my tank and dkh at 9 with some kalk in the ATO so wondering if its just my salt

[bertoni]

I would recalibrate the meter with pH 7 and and 10 solutions. pH 4 calibration might give a bad slope for a reef tank reading. pH measurements are going to be most precise between the two calibration points. At this point, I'd trust the pH test kit more than the meter.

[Kpshc707]

yeah i was going to get some but they where out of the 10 ph stuff funny thing is on the calibration report card that comes with the meter from the factory its calibrated with 4/7 ph and then tested with a 10ph test

[bertoni]

How accurate was the pH 10 test?

[ReefsandGeeks]

Look up calibrating with a borax solution. it's easy and super cheap to calibrate to about 9.2pH. there is a chart somewhere you can find. That's what I do for my meeter and it seems accurate as far as I can tell. IMO, alk is more important than pH in a reef tank, but pH will depend on alk. If pH is actualy jumping around, than your alk may be low.

[Kpshc707]

Thanks ill look into that! On the test they used ph10.01 and it scored 10.0

[bertoni]

Hmm, if the ph 10.01 solution measured 10.00, then the meter might be okay, although I'd always calibrate with pH 7 and 10 solutions in the future. The borax solution can be used as a sanity check, but I personally, would spring for calibration solutions.

7.8 is a reasonable pH for a tank in a house with the windows shut. That level might be accurate, and it's fine, IMO.