Plants for Goldfish Aquarium

I have a 20 gallon aquarium with 4 medium size fantails.
I had to remove all rocks because the goldfish need more room.
I have tried to decorate with a few types of plants - all ended up as delicious food.
I like my aquarium to be au natural so I don't use plastic plants.
Any suggestions on hardy plants that will withstand flourescent light, neutral to alkaline water and hungry goldfish?