The initial question of rams and neons seems to have been resolved, but just for your (Ry4n7) information this combo would not work regardless of the tank size. Temperature requirements are quite different for the named species. Rams must have warmth, 80F (27C) is minimum, but neons being cooler water will have difficulty this warm. Neons should be kept no warmer than mid 70;s F (76F, 25C).
You mentioned soft water, so you have several options for suitable fish in a 55 liter (15 gallon) with the given dimensions. Most "nano" type fish, which are small sized species, will be wild caught, and soft water species are much more common. In addition to the species essjay mentioned, there are the dwarf rasboras in the genus Boraras, all brightly red in colouration. There are many killifish. There are some gourami, like the pygmy sparkling gourami, licorice, eye spot, etc. All of these may be less commonly seen, but depending where you live you may have importers or online.