Those are livebearing fish, don’t know exactly what kind though. They are peaceful and will be good with tetras, danios, minnows, guppies, etc. They breed very easily and in any conditions with zero effort on your end. Just keep the tank clean and they will do the rest.
Gambusia. I take it you caught them since if you had bought they would have been labeled. They are like mean guppies..will attack other small fish. OK to use them in ponds as they take cold water and with bigger Goldfish I guess they can't harm them. Just eat any Goldfish eggs or fry they find.