First link looks good "Red Belly Pacu does due to their size need large aquariums to thrive. Juveniles should never be kept in aquariums of less then 50 gallons (190 L) and adult fishes should be kept in aquarium of at least 200 gallons (700 L) or even better in an indoor pond (or outdoor if the climate permits). Red Belly Pacu does due to their size need large aquariums to thrive. Juveniles should never be kept in aquariums of less then 50 gallons (190 L) and adult fishes should be kept in aquarium of at least 200 gallons (700 L) or even better in an indoor pond (or outdoor if the climate permits)."
Second link: "Maximum size: 60 cm / 24 inches... (Red Belly Pacu) is best kept in a very large aquarium or even better in a pond. This fish scares easily so it is important that you create a lot of hiding places that are large enough to fit these fishes." Ok the size is understated, but the housing requirement isn't.
Third link: "The red belly pacu will grow rather quickly and may reach 12 - 24 inches (30 - 61 cm) if properly taken care of. Given their potential adult size you will need an enormous tank to keep one at home, at least 250 gallons (940 liters). Tank Size : 250 gallon (946 liters) minimum but preferably much larger tanks and ponds. This fish is best left in the wild or in public aquarium displays." Not perfect, but not bad either.
Fourth link: That is wikipedia, even fourth graders know better than to use wikipedia for a reference. But it still says at least 350 gallons.
So if i have this right .... the information you researched said the smallest tank is a 200, but all said a larger tank would be better and a pond would be best.... you have a 220. Did you really think that 20 gallons was enough to justify getting one?
You didn't get bad information, you ignored the information you got.