I'm constantly replacing the veggies because my fish go crazy on it. I try and hide it from them sometimes, lol. Usually I'll put veggies in there 2 -3 times a week. And Just little pieces. Like when your cutting a cucumber to eat yourself, and you cut it into rounds? That works fine. You can do that with the zuccini too, Or cut it long, but then you have rather large chunks of zuccini in your tank and it can get messy. Or just a single piece of lettuce.
You can actually buy little clips with suction cups on them to stick to the side of your tank and put the veggies in the clip. I think it's supposed to be for seaweed, But it works great for this.
You can actually feed them fish food too! They use their foot to form a little funnel thing and will suck the floating fish food of the surface of the water. Or algae wafers, but my fish ALWAYS pigged out on them and my snail never actually got to eat it.
My snail even ate crushed up fish food or finely crushed algae wafers off the tip of my finger. I strongly recommend and mystery snail, they are freakin sweet.