This week we will look at the Fathead Minnow (Pimephales promelas).
This North American native cyprinid may be a common feeder and baitfish, but they make surprisingly good aquarium inhabitants as well! Its golden or xanthic strain is known as the rosy-red minnow. Unfortunately, due to their popularity as baitfish, they have become invasive in many areas. The fathead's invasive status in Europe is cited as the main cause for the spread of redmouth disease among trout and eels there.
These minnows' ability to tolerate a wide range of water conditions allows them to survive in bodies of water that may be uninhabitable to other fish, such as waste drainage sites. It has also been studied to investigate the effects of these waste materials on aquatic life. This species is well known for being studied for possessing an alarm substance, known as Schreckstoff. This substance is released by injured fish, which alerts other minnows to seek safety. Fathead minnows learn to recognize an animal as a potential predator when they detect the alarm substance in the water, or the substance consumed by the predator. Prey fish with these chemical predator recognition abilities can inhabit areas with low visibility and more quickly detect ambush predators like the fathead minnow's primary predator, the northern pike.
Like many cyprinids, they eat just about anything from crustaceans and algae to detritus. They prefer a neutral to hard pH and cooler waters (50-70F or 10-21C). They need to be kept in schools of 6 fish or more, ideally in a 20 gallon or larger. They can be easily bred in the aquarium and are one of the only cyprinids to guard their nests (carried out by the male). Lifespan ranges from 2-4 years depending on if they have spawned and they usually grow to be about 3 inches long (7.5 cm).
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