Snails can be a blessing or a scourge, depending on the type.

They clean away debris as well as add interest. If you own fish, however, they will most likely eat them into extinction. You can still have them in your streams, however. Because snails feed on debris, be warned that they will also bring any disease they come in contact with to your pond, so be advised of this before you take snails from natural waterways.

Snails are also sold to eat algae, and they do that in fish tanks with plastic plants. Many sold in pet shops and in pond shops also eat plants. Apple snails and Columbian ram's horn snails are voracious eaters. They will attack waterlilies and other pond plants.