Rube_Goldfish

Ah, I didn't think of trying to get pre softener water! Now I'll have to to pull out the manual and see how to do that... Thanks!

I'm still pretty new to the hobby; I have a ten gallon tank that's been running since the beginning of September 2021 and has had fish in it since early October 2021: two honey gouramis and five cardinal tetras (down from an original school of six). My nitrogen cycle numbers are fine (consistently 0/0/10-20 ppm), and while I know my pH (8.2) is high for cardinals, it's very stable, and they haven't seemed to mind it too much. In mid-November 2021 I put a nerite snail in the tank. It just sat there that first day; I saw it on the glass the next morning, but by the end of the second day it was down on the gravel and never moved again. In mid- and late-December I tried again, adding three Amano shrimp and one nerite snail, respectively. I found one of the Amanos on the floor the morning of the second day (no lid; I've since added a pretty snug lid). The other two Amanos seemed fine for about two weeks or so but have since disappeared. I haven't seen them in about two months. I know they're very good hiders, but I'm not optimistic that they're still alive. The second nerite followed the pattern of the first one and also died within about 24-36 hours. With all that long preamble, I bought an API GH/KH test kit and followed @Irene's advice on her YouTube video on pH/GH/KH, having theorized that that was the problem. I ended up with a GH of 3 degrees and a KH of 14 degrees, and the pH is still that constant 8.2. I have a water softener in my house, so I guess that's why the GH and KH don't "match". I bought some Wonder Shell from the Co-Op to increase the GH, because I'd like to have snails and a couple Amanos in this tank (which I will shortly be upgrading to a 29 gallon). So here are my questions: 1) Is the low GH the source of the problem I'm having with inverts? 2) If so, will Wonder Shell help? 3) Does Wonder Shell affect pH or KH at all? 4) Would raising the GH with Wonder Shell hurt the cardinal tetras and/or the honey gouramis?