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Synonyms for Topminnow (same or very similar meaning)

WordNet sense 1 (small usually brightly-colored viviparous surface-feeding fishes of fresh or brackish warm waters; often used in mosquito control):
live-bearer, poeciliid, poeciliid fish

WordNet sense 2 (freshwater fish of Central America having a long swordlike tail; popular aquarium fish):
helleri, swordtail, Xyphophorus helleri

From the ODE community, based on WordNetadd/edit