The situation in the video you posted, that is not yours but someone else's tank, is stable and neither gar nor RTC can swallow each other and they have been together long enough to know this. The Pangasid in the tank won't last, my prediction is. Not to downplay personality factor, fish of the same species can behave vastly different, especially because of their prior history.
The Gar may feel the RTC is a threat.
What's your basis? I'd never think that. I guess unless RTC tried swallowing the gar but even then the gar wouldn't bite but try to run away. I could be wrong and open to be taught.
I suggest you rehome one of them. The Gar and RTC will outgrow that no time especially the RTC.
With all due respect, this is not our first run in with the RTC_Keeper. He surely seems the one who learns from his own experience best of all. Let him do that and also stay on topic. No fish = no problem. No woman, no cry. I don't believe this is the point. We'll never learn anything or learn much that way. Getting rid of fish is not the answer to all fish-keeping-related problems we experience. We all started somewhere. Let the guy have his start and learn, I reckon and suggest. He doesn't want to start with pictus catfish or pink tail chalceus. Obviously. Let him start somehwere.
Both species deserve to be housed in a large Public Aquarium or a large pond.
Maybe, maybe not, but let the guy live and learn, I humbly propose.
No they are saying that the RTC and the gar going to outgrow your aquarium.
Yes, but in my humble opinion this is immaterial at the moment. This is not the question and at the moment the tank is more or less adequate sizewise.
The main reason for attacking the RTC is probably because the gar feels he has no space.
Can you substantiate this? AFAIK, gars are not territorial creatures. They can be aggressive but not for territorial reasons whatsoever. I think this is a predation motivated attack, especially if it happened in pitch black at night. Gars in general will take a swipe at anything that moves in their tank until they learn that there is no living body in their tank that they could eat. It will take time.
