Do goldfish show more tendencies to eat plants as they mature, or will a juvenile pretty much display its plant munching habits early on? I ask because I am considering getting my fish young, adding them to the tank, and trading in any garden grazing fishies for others until I have a set of fish that are pretty well behaved. Any opinions on how well this would work? I would of course plant the tank with recommended goldfish plants in the first place, and also let them get fairly established before adding fish. I'm looking at a combo of fantails, ryukins, and moors.

If I leave them an open area at the front of the tank to dig, are they more likely to not dig in the heavily planted areas?

well i don't tihnk it is as much as the fish u get or what age as what type of plant it is. like i have a amazon sword and sum other stringy thing (forgot the name) and my black moor who is about 1.5 inch long doesn't nibble at all neather do my minnows ( 18 gallon tank). i just added sum moss balls and all my moor does is poke them and stuff (it's gf nose soccer). i heard they don't munch on anubis eather or java fern or java moss. i am getting sum java moss and anubis on friday i will tell u if he eats them.

I've been reading various people's accounts with goldfish and it seems like some people have luck with them and some don't. Apparently some goldfish even eat the "goldfish safe" plants.

my goldfish (3 orandas) nibble on the anubis, and antother single-stem plant i have, ( not enough to harm the plants) but they seem not to like the java moss b/c they are always spitting it back out.

I think goldfish can develop a taste for plants at any age. Mine prefer to root around in the heavily planted areas, because stuff gets caught around the plants and they like to check it out to see if its edible.