Red Hook Silver DollarsOrigin: These species of silver dollars can be found schooling throughout the Amazon Basin in South America. They can be found in slightly acidic, moderate moving rivers with dense vegetation and bogwood. Tank Size: 80 Gallon+ Swim Region: All over Temperament: Peaceful; Community fish Size: 9 inch (Males Females) Temperature: 75 82 F Water ph: 5. 5 7. 5 Water Hardness: 5 15 dGH 89 267 ppm