Their population will basically follow the availability of food in the tank. You could provide them places to hide to safely reproduce but if there are no predators (certain fish etc..) in the tank then they should do fine either way. Some people breed them for specific fish which is pretty easy.. but if you don’t have a mouth to put them in specifically then I would let them just do their thing :D
As far as moving them to your main tank you can suck out the tank water and siphon them out. Unsure what you would use as a filter material but I know people do it here haha
