How to Breed a Western Mosquito Fish to a Guppy

Koi ponds are effective habitats for mosquito fish.

Western mosquito fish are aggressive, live-young-bearing fish that enjoy feeding on the larvae of mosquitoes. Introducing the mosquito fish to waterways and ponds for mosquito control can be problematic because this species will displace other natural fish by eating their young as well. However, in an outdoor koi pond they function well to keep the pond free of mosquitoes. The koi fish young are too large to be affected by the mosquito fish. Just be cautious: The mosquito fish will eat its own young, so care must be taken when raising the fish to a guppy.

Things You'll Need

• Main tank or pond
• Tightly woven fish net or tank net
• Breeding tank
• Water filter
• Thermometer
• Tank heater
• Fish food (prefers bloodworm and live foods, but will eat powdered flakes)

Instructions

1. Fill your main tank or pond with both male and female mosquito fish. They should begin to breed soon, as mosquito fish breed all year long.

2. Observe the adult fish in your main tank or pond. When females display their gravid spot, a dark patch on the underside of the fish near the tail, they are pregnant. These fish breed all year long and many times per year, so check often.

3. Prepare the breeding tank. Attach the water filter and plug it in. Install the thermometer and adjust the tank heater to keep the water between 60 and 90 degrees Fahrenheit.

4. Isolate the pregnant females in the breeding tank.

5. Feed and care for the females as usual and wait until the females give birth. As one gives birth, return the female to the main tank or pond. The females will feed on the young, so isolate them rapidly.

6. Continue to care for the fish in the breeding tanks as you would adult fish. Mosquito fish grow to maturity in about six to eight weeks. You may lose later birthed fish to the younger birthed fish unless you use additional tanks to isolate each pregnant female.

7. Return your guppies to the main pond.

References

• The Guppy Site: Western Mosquito Fish
• The Aquarium Wiki: Gambusia affinis
• Absolute Astronomy: Mosquito Fish