I keep mine at way smaller tanks atm. They don't do well in very big tanks while still small ime. They tend to eat more in a relatively smaller tank. What matters is the water flow. Power heads/wave makers. Also, some are skittish and some are not so skittish.
Honestly, i don't think a river monster size gatf would ever be seen from a home aquarium (unless wc). And a fish that size in the wild would probably be very old considering how slow they grow.
I think they are quite easy to keep as long as u got good water, enough flow and food and ample space relative to the size. With regard to them being skittish, they would more likely be but some are not as bad. Tankmates may outgrow them or be killed by them. But at the right size they may be communed.
