Don’t assume your CAE will live only off algae. Feed him veggies, algae wafers and other sinking food. Mine also adores shrimp pellets and frozen brine shrimp and to a lesser degree, blood worms. I know I’m in the minority (or maybe the only-ity), but I like my CAE, he has been a great fish for 11 years, has never attacked anything and still eats algae – or at least is still rasping on the tank walls, plants and rocks. When instances of plecos or otos attacking fish happens, they are defended because they have been improperly fed – when a CAE does that, he is just labeled as bad.
I’m sorry, I do not know the size of your tank? The only problem I can see is that you said you have CAEs – plural. They are territorial (not unlike cichlids but in cichlids it seems to be understandable, in CAEs it’s not tolerated). Do you have caves for them? They like caves and perhaps if each had its own, you’d be OK, although I’m not sure… I’ve only ever had one CAE in a tank.