Keeping veggies from floating... what's the trick? lol?

So I have been feeding my fish/snails fresh cubers and they love them but there always floating. I know they sell the little clips with the suction cups but I live in a small town and haven't had a chance to get any so until I do, any tips on how to weight down the cuber slices with something that will not hurt my fish but will keep the snacks at the bottom of the aquarium? Thanks!