Keeping A.australe with F. gardneri? I've tried that many times. AUS can be an aggressive fish, even to each other. Those perfect specimens you see with long trailing caudal filaments were usually raised alone, but in close quarters (like 30 young in say, a 15g, they eat to nip these caudal streamers off which is why there are so many photos of ones with truncated tail plumage.

Long straight filaments mean they're original. Long filaments with a bug of a kink in them mean they were bitten off once and grew back unimpeded.

Only very young fish don't have filaments but they look like fins that are still growing.

Where there are ragged stubs they've been repeatedly nibbled off.

So,if you want perfect specimens you need to grow them individually.