who ate all the plants??

[veetee]

I've searched the forum for a thread which might give me the info, but so far haven't found any. My plants are getting nibbled big time, especially the wheat grass. Is this because the fish are hungry? They get a small pinch once a day, should I be feeding them more, or or do they just like to eat the plants regardless!
I only have 3 cherry barbs and a silver shark at the moment in a 20 gallon, 4 plants all different (1 floating) and they are nibbling them all, but seem to have taken a particular liking to this one. Is there any way of stopping / reducing the damage, or do I just have to put up with it??