I find that frequent rinsing and an intial soak with a little hydrogen peroxide in it is key to mold prevention. and good drainage! but, that said, if I have some that gets a little mold on it, if it's just small sprouts, not really grass, I'll dump it into my ferment bucket. Pretty sure that the good bacteria in there will take care of any (minor) mold problem. if it's reached the grass stage I tend to tear off the worst part, soak the whole kit and kaboodle in ACV and water to kill mold, rinse well, and feed immediately, even if it's not as full grown as I'd like. That way I'm not wasting feed. I mean, I could compost it, but that would be kind of counterproductive since my chickens favorite spot in the yard is the compost pile... Frankly, as long as you're checking a couple times a day to spray it, it should never really get out of hand.