Killifish and rice fish are captivating species that bring vibrancy and dynamism to freshwater aquariums. Killifish, from the Cyprinodontidae family, boast striking colors and patterns, with over 1,270 species inhabiting diverse ecosystems from the Americas to Asia and Africa. Adaptable to both stagnant and flowing waters, they are a versatile group. The Japanese rice fish (Oryzias latipes), a small and resilient species from East Asia, is often found in rice paddies, displaying semi-transparent bodies that can shimmer in hues of orange or gold. Both killifish and rice fish exhibit distinctive breeding behaviors and are relatively simple to care for, making them attractive to aquarists desiring to enliven their tanks. Killifish may need more care due to their specific habitat requirements, while rice fish are easier to keep, with the caveat of a clean, well-filtered environment. For killifish, optimal aquarium water parameters include a temperature range of 68°F to 75°F (20°C to 24°C), a pH level of 6.0 to 7.0, and total hardness of 7° to 10° dGH (120 ppm to 160 ppm). Rice fish, or medaka, thrive in temperatures from 61°F to 75°F (16°C to 24°C), a pH of 7.0-8.0, and water hardness of 5-15 dGH. Regular monitoring and maintenance of these parameters are crucial for the well-being of your fish.