you would be fine with that mix, unless you have an unusually aggressive gar or lima. I kept a polypterus palmas for year and him and my much larger (18") spotted gar shared the same tight hiding spot. Also in the tank was a tiger shovelnose. Currently have P. senagalus senagalus with a TSN, spotted gar, royal clown knife, silver dat and a silver aro. Most fish tend to ignore polypterus and let them do their own thing, unless there is a significant size/temperment difference. Also, the tank would have to be quite large to accomodate the potential size and swimming habits of a fl. gar. Good Luck!