These cute snails are more expensive than the other nerites because we have a hard time getting them. And, be prepared to receive small snails and watch them grow. These will only grow to about the size of a marble, and will not crawl out of your tank. One of the other reasons people choose Nerite snails is because they won't reproduce in freshwater. They are like salmon...and make their way to saltwater to breed. These are excellent algae eaters and will keep your glass, ornaments and plants clean. They don't burrow. Nerites will be more active when warm, but will survive cold temps. They are very hardy.