The gar will work in any non aggressive fish, they are huge wimps who get bullied easily by rambunctious fish. any non aggressive fish too big for him to eat will be fine and too big to eat is probably smaller then you think, an 18in gar most likely wont go after anything bigger then 5inch as long as he is regularly fed.I was hoping to be able to get a black wolf fish with other fish well. From what I have heard this probably won't work so I was thinking either a shortnose gar with a couple odoe pikes if they would work together and a cat or two. Or a jardini arowana with a couple odoe pikes red tail cudas and a cat or two if the shortnose gar doesn't work with the pikes. Any suggestions?