That settles the pH issue. The actual pH of your tap water is 8.2 so you now know that.
The GH depends upon the fish species. Generally speaking, there are fish that must have moderately hard or harder water--livebearers, some rainbowfishes, rift lake cichlids to name a few--and these assimilate the calcium and magnesium from the water which continually enters the fish. Then there are the soft and very soft water species that do not need any minerals in the water, and will be better without. They have evolved with a physiology to function best with mineral-poor water. In the middle are a number of fish species that may occur in soft water but can manage with a moderate GH.
The GH is the most important parameter (aside from temperature) and 55 ppm [= 3 dH] is very soft water. Forget any of the hard water fish mentioned abo0ve, they will not survive. But most all of the soft water species (tetras, rasboras, danios, barbs, catfish, loaches, gourami, dwarf cichlids) will be fine.
The KH at 170 ppm [= 9 dKH] is a bit high so the pH will not likely lower much, but once the aquarium is established this will work out. It is best to leave the pH alone, a fluctuating pH is more of a problem for fish that a stable one. The only way to lower the pH is to reduce the KH, and this means diluting the tap water with "pure" water, but I would not start down that road yet. If you can use your source water as it is, it will make life much easier when it comes to water changes.