Most of my other fish go after my pleco's wafer too, despite having already gotten their own food or treats (grrrrrrr!). I put two wafers in sometimes, but I've also discovered that my pleco sometimes decides to be really protective of his wafer and chase the others away. It's probably very annoying for him to have to defend his food, but it's also really cute! Sometimes, he just covers it with his body, like, "Back off, I'm saving it for later!!"
Good idea with getting some zucchini too! There should be plenty of that to go around, so your pleco shouldn't be shut out from that. My pleco doesn't always get much from his wafers, but he always gets plenty of cucumber when it's in the tank.
