When are you thinking of starting a 100 gallon tank?
Okay. I did a bit of reading on the web today and the conscenses is that the folowing plants usually do get minimal nibbling from gold fish. (some get a bit more, but grow fast enough to keep up) Some of these you already have in your tank.
Java Fern, Java Moss, Anacharis, Hornwort, Vallisneria, Anubias, Water Sprite, Marimo Balls (supposedly good for using up access nutrients keeping algae at bay) Crypts and swords.
The plants that need substrate can be potted and cover the top with a mesh liner to keep the goldfish from uprooting them. The more plants you plant at once the better because from what I've read, the goldfish don't know what to do (or where to start LOL) with all the plants!
I laid out a few ideas on paper. You might hate the scapes, but hopefully they can get you along in designing your scape.
the scapes look better at a distance...the colors get distorted in the closeups
There ya go! Hope this helps
I have more to share with you about the bare bottom but I gotta get to bed. So tired. Night!