Remarks: The Least Killifish (Heterandria formosa) is the smallest live-bearing fish species in the world and is also native to the United States. While their common name calls them a killifish, these fish are not actually killifish and belong to the family Poeciliidae which includes other live-bearers such as guppies. They are a shoaling fish so should be kept in groups of 3 or more. Least killifish inhabit shallow, heavily vegetated areas of still or sluggish waters so lots of plants and little to no current are needed. They have been recorded living in brackish conditions but thrive best in freshwater. Females are much larger than males have rounded bellies. In fact, it is rare for males to exceed 0.5" in length. Due to their small size and peaceful disposition, it is important to not house these fish with large, aggressive species. Scientific Name: Heterandria formosa Common Name: Least Killifish Max Size: 1-1.5" pH: 7.0-8.0 Hardness: Soft or hard Temperature: 64-82F Aggressiveness: Peaceful Region of Origin: United States Captive Bred or Wild: Captive Diet: Flake, baby brine, or very small powder food. Compatibility: Small, peaceful community fish and small catfish Tank Mate Options: Swamp Darter ”Green Swamp” (Etheostoma fusiforme) Three Line Pencilfish (Nannostomus trifasciatus) Mystery Snail (Pomacea bridgesii) *****Please review our Shipping and Handling FAQ prior to placing your order. It contains important information about order fulfillment time, shipping speed, and other pertinent details.*****