I have two very small bristlenose catfish, and they seem to like the zuchini.
I also have a sailfin pleco about 8 inches long and he just loves zuchini, the first time I gave it to him all he did was eat and eat.
As for leaving it in there I wouldn't as it will pollute your water, I leave mine in for one day only and then throw out whats not eaten. Even leaving it in for this length of time causes some of the zuchini to float in the water.