Royal plecos have the potential to reach 18"+. They are mainly vegetarian. They NEED driftwood in the tank. They create more waste than any other pleco I have owned. Very slow growth rate, like an inch a year give or take. The dull eyed royal is supposed to only grow to about 9". Blue Eyed panaque I cannot afford so you'll have to look for personal experiences elsewhere for that one! Although I believe they have similiar care requirements as the royal and will grow to 18"+ also.