entirely dependent on the temperement of teh acara in question , some are fine , others like my old female are nasty so and so's . with a mellow acara it could work but if you get an aggro one those rams will get battered .
I'd say no due to the difference in size. If you have a very large aquarium in which the smaller fish will seldom come into contact with the Acara then I'd say yes.
she just did not want then to have the spot light to them self haha. But I found mine to be great with smaller fish she could not eat. But I found blue acaras to be more aggressive with fish there own size. Like they never got along with my keyhole well. When blue acaras are kept with larger fish they are very good with bigger fish.
In the right size tank with the right fish it can work.
I have voted yes, but my proviso would be .... only in a tank bigger than about 60G (250 litres). WIth enough space, virtually anything will get on.
Might work in a smaller space but the chances will reduce.