Just how big can a mystery snail get?

Biggest I've seen was about the size of a tennis ball. They are called apple snails for a reason!

I've heard that one of the types of mystery snails is known to reach softball size, but the ones I've seen are only about half that.

mine's on it's way. It's probably the size of a plum right now. He will eat every plant you leave in the tank. we feed him fresh lettuce. He'll eat a whole leaf of lettuce in minutes. We bought a gold and a black mystery at the same time. The gold was about 50% smaller than the black. He is now 4 times the size of the black. Kyle