Easiest way to breed ramshorns is to:
1. get a small tank
2. put a small heater at 24-26
3. bare or sand substrate
4. add snails
5. add food(fish food, vegetables or dead plants!)
6. do frequent water change or add a small filter
7. add more food
8. Baby snails
and yes i wouldnt put them in a tank if your trying to breed fish. Ramshorns are excellent puffer fish food and a good clean up crew that adds colour to your tank(if they are red)