Conches are not a good choice to go into a brand new tank IME, as they are not the hardiest of gastropods and they run the risk of struggling for food in a new tank unless you're planning on target feeding. Conches can be a great addition to a tank (not just as a janitor) and I love them, but it's safer to wait until the tank is more established before adding one. To be honest, I'm skeptical of cuc packages that include anything but hardy stuff like hermits and/or Turbo genus snails, since dumping a large variety of less-hardy stuff in at once is pretty much the opposite of building things slowly and safely.