You could always just leave a pile of fish flakes in there, it'll just be a bit of a mess to clean up. I forgot to ask, when you say apple snail do you mean Pomacea bridgesii? There is Pomacea canaliculata commonly sold as mystery snails. You do NOT want this snail, they will eat live plants and will grow to be huge. I'm not kidding when I say huge, like probably bigger then your fist. Pomacea bridgesii stays fairly small and only eats the dead plants if no other food is provided. Best of luck to you and your future snail! You made a good choice, they are awesome pets. If I have like powdered algae wafer on my finger, he will lick it off. It's sweet.