I haven't tried any cucumber yet, but my betta also loves to go after algae discs. He doesn't actually consume them, but he bites and tosses the disc around, spitting out anything he gets in his mouth. Seems like he is just playing more than anything else, or intimidating.
He doesn't do it with Rapashy Community Plus though, and my snail loves that stuff.
Also, your snail might be going for calcium deposits on your tank that are very difficult to see. I see mine going to the top to clean glass above the water level where it's more concentrated. Calcium is important in a snail's diet, which is why im told zuccini is the best fresh vegetable for them.