4 Large Black/Purple Mystery Snails (1/2"-2"+) Algae Eaters, Cleaning Crew Safe for Fish, Plants, and Shrimp Mystery snails are a freshwater snail that help keep keep your tank clean by eating algae and left over food particles Black/Purple mystery snails have a dark shell and a black or purple body making them stand out among all other mystery snails A freshwater snail that keeps tank walls clean and are a blast to watch explore your aquarium A very popular snail that can grow over 2 inches and is very easy to care for. A very active snails that goes great with other fish or shrimp