I usually feed my pleco zucchini (seeds removed) and I can get away with leaving it in up to a day and a half without it fowling the water. I ran out of zucchini about a month ago and decided to give him whole broccoli. By the next morning my water smelled terrible, like s*** and after I removed the broccoli i got a bacteria bloom and the water turned milky white. I'll never again put whole broccoli in.