| One snail like that would eat the whole cucumber in a matter of days. Varying the diet with other veggies fruits and algae disks is best so one thick slice of cucumber every 3 days along with zucchini squash and any other veggies or fruits (blanching or investing in a veggie clip is also recommended) . Make sure you wash them well, and watch your parameters closely your nitrates can increases quite fast due to the decaying fruit or veggie depending on the varicosity of your snails and their diet. | 
Similar Aquarium Fish Forum Threads 
I like your snail, too. I didn't know shrimp liked the veggies too. 
