I have amano shrimp in a tank that I always add salt to just for my fish's health and these shrimp have been in there for a year and one or two always have eggs with them. No problem with them living. The only problem is with fish eating them. I would just try adding the recommended amount of freshwater salt and see if that does it. Also you can read all u want about ph, salt, temp., etc. for fish breeding. I have fish and inverts breed in almost totally different conditions than suggested. Just keep em happy and in good, stable and nonstressed conditions and it will happen
