Welcome to MFK!!!
They can get along fine unless and until the mbu decides it doesn't like something about any tankmate.
I have a pair of 1 footers that are fine in the 650 with a bunch of FW tarpon. However, keeping any sedentary bottom species will likely result in many 'test nips' from the mbu on it's bottom-dwelling tankmates. The tarpon are fine (for now) due to being active constantly moving fish. The tarpon will remain fine unless the mbu decides they're in the wrong place. At that point, I just hope I'm around to pull and relocate any survivors.