make sure your gar is big enough to take care of itself...since the pacus are fast growers you want your gar to have the head start. Plus if its too small your gar may be split like a twig by the pacus mouth if not taken cared of right...but it should work...but its still risky with a more fragile fish species. Pacus are more robust and powerfull fishes that can break open a hard shelled nut and can go easily with a gar as a twig
lol. pacus are not amoung my favotite fish. all mine ever did was steal my gars food and nip at their fins. but i guess they are ok if they have their own tank.