Vieja maculicauda are highly aggressive (as said above) herbivores, the most far ranging Vieja species in Central America , Mexico to Panama.
They will easily attain 14", and get lots of red color if cared for properly.
Put them in a large tank, 6 ft would be considered minimal, and even in that size tanks territorial disputes with other Vieja. can become lethal.
Here in Panama, they are often found in deltas, and in the sea grazing on marine algae.
When I kept them, I feed a variety of pellets, some made for salt water vegetarian species, that combined Spirulina and plenty of other marine green and red algae.
I also fed sheets of nouri and others made for sushi.