Of the three parameters, GH, KH and pH, the most crucial for fish is GH. This is the level of dissolved calcium and magnesium in the water, the minerals that determine "hardness" of water. KH does affect fish, but in my experience this is less of an issue. The pH also affects fish, but this is secondary to GH provided the pH is not extreme, or fluctuating.
The terms we use are subjective, but his chart is one I worked out from several sources a few years back:
0 - 4 dGH [0 - 70 ppm] very soft
4 - 8 dGH [70 - 140 ppm] soft
8 - 12 dGH [140 - 210 ppm] medium hard
12 - 18 dGH [210 - 320 ppm] fairly hard
18 - 30 dGH [320 - 530 ppm] hard
over 30 dGH [over 530 ppm] very hard
With the possible exception of the Rummynose, the fish mentioned in post #7 should be fine, according to data on Seriously Fish. I cannot explain the difference between your GH and KH numbers, but other members have mentioned similar and I believe it is not necessarily inaccurate nor impossible (something I learned). You should be able to confirm them with your municipal water supplier. KH is sometimes termed Alkalinity; if it really is this high, the pH of the source water will not lower, but 7.4 is not unworkable.
The terms we use are subjective, but his chart is one I worked out from several sources a few years back:
0 - 4 dGH [0 - 70 ppm] very soft
4 - 8 dGH [70 - 140 ppm] soft
8 - 12 dGH [140 - 210 ppm] medium hard
12 - 18 dGH [210 - 320 ppm] fairly hard
18 - 30 dGH [320 - 530 ppm] hard
over 30 dGH [over 530 ppm] very hard
With the possible exception of the Rummynose, the fish mentioned in post #7 should be fine, according to data on Seriously Fish. I cannot explain the difference between your GH and KH numbers, but other members have mentioned similar and I believe it is not necessarily inaccurate nor impossible (something I learned). You should be able to confirm them with your municipal water supplier. KH is sometimes termed Alkalinity; if it really is this high, the pH of the source water will not lower, but 7.4 is not unworkable.