Ah okay it says 3 gpg Iām not sure what that measurement is, they state it as slightly hard on the website?
The two units most often seen in the hobby are ppm (parts per million) and dGH or dH (degrees German or degrees hardness). We like to use these on this forum because they are the hobby standard units, and converting is simple. And for the record, ppm is identical to mg/l (milligrams per liter) which water authorities often use, though not all of them.
To your 3 gpg (grains per gallon). One gpg is 17.1 ppm so 3 gpg is 51.3 ppm.
Converting ppm to dGH and in reverse uses 17.9 and you multiply dGH by 17.9 to get the equivalent ppm, and divide ppm by 17.9 to get the equivalent dGH. I mention this because again you come across both scales, and some of us like smaller numbers or larger numbers, so I always like to give both.
So 51.3 ppm divided by 17.9 is 2.8 dGH. Usually we round up/down as it is not that critical so this is 3 dGH. This is very soft water. So you see why I insisted on the number...terms can be very misleading depending who is using them.
Where all this brings you/us is...you want soft water fish species. Those already mentioned are soft water species. Avoid any harder water species such as all the livebearers, some of the rainbowfish, rift lake cichlids. There may be a few odds and ends, but it is quite easy to stay with soft water fish because these include most of the species from South America (tetras, catfish, etc) and SE Asia (barbs, danios, rasboras, loaches).