Bottom line is as @Greggz
mentioned: pH 7.6 and dKH 5 makes sense for expected CO2 levels after allowing for degassing. Now, as to why KH and GH are rising after a day or two of different tap testing points, I have no idea: it shouldn't. I'd suggest the following:
Retest, but make sure to measure the tap water that is being degassed, before degassing it, i.e.; run both tests on the same glass of tap water (and make sure the API kit hasn't expired). I'd also increase the sensitivity of the tests by using 5x the amount of sample water for the tests, then divide the resulting measurements by 5.
Yes, itís the crazy gH spike that baffled me. I repeated the test twice (on the same aged water) just to be sure. It made me doubt all of my other readings, honestly, except my 75 gallon results are still stable.
But Iíll test it again, and your suggestion is a good one. I use the API liquid tests for all parameters, and they are all less than 2 months old, and not close to expiration.
But...even assuming my aged tap water isnít too bad, it still seems to affect the shrimp. Why? I dunno. Iíll keep trying to figure it out, but it has made me really want to try using remineralized RO water to see if it helps at all.
I really appreciate everyoneís input and help! There are so many nuances to keeping these crazy crittersóI feel like no matter how long I have them, Iíll always be learning something new (and thatís a big part of the fun for me!).
Bump: FWIW, I wasnít able to get the TDS pen tonight as I had planned; my LFS stopped carrying them for some reason so Iíll have to wait for a delivery from Amazon. Could TDS maybe be the culprit?
And actually, while Iím on the subject...TDS is something I donít fully understand. Total Dissolved Solids, yes, but that could be anything, right? So what exactly does a TDS in a tank represent? Is a high TDS always a bad thing? I would assume theyíre higher in heavily planted tanks?
Iíll go down the Google rabbit hole on this, but the problem with the Ďnet research for me, so far, is all of the wildly conflicting info when it comes to shrimp. Iíve lurked here long enough to trust you guys, so I appreciate you humoring my both my newbie ignorance & my enthusiasm! 😁