I do both, depending on what I'm feeding. I'll let crickets run loose but put roaches and worms in a cup so they don't escape. That way they get the best of both worlds but I don't have to worry about the roaches hiding in the plant pots for weeks or months. The crickets I don't worry about being loose, personally, because if I feed early in the morning it's highly unlikely that any will be left by the time night hits. And if any are left, one or two aren't going to be a big threat/danger to a healthy animal.