I am currently housing a clown knife and 3 florida gar in the same tank, other than the occasional stand off and bumping, there is no aggression between them
Oh... nope... they can't swallow 99% of tankmates because their jaws allow for a very small gape. Even big gars can't eat many small fish. That does not stop them from killing them though.
My gar have a bad habit of gutting/skinning the feeders i put in from time to time for Gary(the big florida). They are WAY to big for most of the gar(gary is 18" the biggest of the rest, is a mere 16" and half as thick if that)