What are the tank's parameter for your Goldfish?
Temp range, lighting,
pH?
I would almost bet that Goldfish would tolerate/ignore Anubias Barteri. These plants do well in a wide range of temperature, light and pH. I have a beautiful Anubias Barteri in my
chiller cooled Rainbowfish tank (74-76F), at the lower
WPG area and it is thriving. Keeping it clean might be another story... I don't know about Goldfish, Koi or alike keeping, and this is a question I have: Do they tolerate Apple Snails? If they do, then keeping the Anubias Barteri clean will be their job to do.
On the other hand, if your Goldfish are used to moderate lights, or if you can manage to upgrade lighting at desired spot in your tank to say 2 to 3 WPG, you could try Amazon Swords or Black Swords, these would adapt to the lower temp just grow somewhat slower, which isn't a bad thing after all.
Anacharis and surface-floating plants is what I used when I once kept Goldfish in a pond I had (from age 16 to 23) I recall water Orchids, water lettuce, duckweed... then again, I live in the Caribbean so not sure if that would work in other latitudes.
Pepe
Santo Domingo