topminnow

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

(noun) freshwater fish of Central America having a long swordlike tail; popular aquarium fish. Synonyms: swordtail, helleri, Xyphophorus helleri.