currently, I have 2 tanks with bichirs
one is a 125 w/ 5 12-14" bichirs and 2 13-14" gar
the other is a 210 w/ 4 6-8" bichirs, a male and female motaguense @ 4", a 3" oscar and an 11" BGK. Had a couple 7" tigs and a couple 4" hystrix in with them for a long time, too as well as many other fish in the past.
bichirs get along w/ just about everything. Gar don't go well w/ too many fish, so that's why it's only bichir and gar in the 125. That and it's almost overloaded.