With a Peru piraiba, you might be okay with a 1000 gal enclosure for 5 years, if my experience were of any guidance... Still I'd say this is a minimum, and a minimum doesn't mean nice, it means barely adequate. They love swimming, which makes for a much larger minimum tank size.
I am keeping a Peru in a 4500 gal at 2.5' and another Peru at the same 2.5' in a 240 gal temporarily and out of necessity, because it was getting bullied badly in the 4500 gal. The one in 240 gal feeds and doing ok but I can tell it is miserable and has as if bouts of anger as if trying to get out, swimming wildly and bumping into walls. The tantrums don't last long but are heartbreaking to see.
I'm no expert on Suriname versus Peru babies.
GiantFishKeeper101
is one expert.
Rpul
dazzapolypterusweeksii
I'd say first and third pics are of Suriname, second pic is of Peru.
Dorado catfish are extremely hard and demanding to house and raise. They do best alone or with VERY carefully chosen tank mates. Yes, at some point in time they start needing 10x more space to swim around versus even a piraiba, or perhaps a round or oval enclosure might solve this problem also. So they swim stubbornly against a wall for weeks or months on end. In my experience anyway. Then eventually stop. It probably has to do with their seasonal migration mode.
They don't only swim against a wall or sit. Ours swims laps leisurely too or swims against the current treadmill-style.