I use NLS wafers and they are good for a couple of days- they don't disintegrate or cloud the water.
As for veggies- things like the stems from asparagus, broccoli and cauliflower, peas, zucchini, cucumber I leave in for 24-36 hours.
Fruits and soft veggies I just leave in overnight.
Some fish like their veggies when it is starting to, well... Accumulate a nutritious biofilm.
It can take ages for them to decide to have a taste, and some prefer different parts if the fruit/veggie. I have a pleco who I slice cucumber lengthways for- he hoovers up the soft flesh and seeds and leaves the rest for the bristlenose. They consume most of the rest, including the skin, and then my kuhlis and cories finish off the 'matured' dregs.