do plecos eat plants?

do plecos eat plants?  I think that mine have discovered the tender leaves of
my plants.  I have two Amazon swords and two plecos about 3" and 4".  It
seems that they have eaten the outer layer of the leaves and left the leaves
transparent-ish.  Are there any other fish that I can trade these guys in for
that will only eat green algae off the glass and not touch the plants?  I
know about oto cats, but they aren't at my local fish stores and I know that
they aren't very hardy.  I want hardy algae-eating only fish.  Also, these
plecos are really pretty.  Is there any way I can prevent them from eating
the plants?  I fed them algae wafers, but my zebra danios pick up on that.  I
give zuchini slices (boiled until they sink) as well (zebras don't touch
that) but they go right back to the plants too.

Thanks in advance.