Piranha, the name of a blood-thirsty fish that often strikes fear into most people’s hearts, is often depicted in movies and literature as a savage killer.
But the pacu piranha, often confused with the red-belly piranha, a near-cousin, is more of an omnivore, preferring vegetation over meat.
At an early age, two to six inches in length, it is very difficult to tell the two fish apart. Both have a reddish breast, with a glimmering, silver body shape, but as they continue to grow, the difference becomes quite apparent.
While the red-belly piranha will maintain its red underside, the pacu will lose the color and replace it with a stone grey and silver appearance.
But the color is not the only difference. Unlike its cousin, the pacu grows at a very rapid rate, often exceeding 12 inches in a single year. On average, they will grow to 28-30 inches if provided adequate food and space. Not your average tropical fish by any means, and certainly a fish requiring a very large aquarium.
The other big difference is the teeth. We don’t usually think of the teeth as a means of distinguishing one type of fish from another, but a red-belly piranha will sport short, razor-sharp teeth, while a pacu will have teeth more like a human beings’ molars. Their teeth are often compared to a cow’s teeth. Teeth that will work well to grind massive amounts of vegetation.
I’ve raised both red-bellies and pacus and I can tell you, they are as different as night and day. (I raised red bellies when I lived in Ohio).
Red belly piranhas are prohibited in the state of Florida, but pacus are perfectly legal and sold in most pet shops. Both require tropical conditions to survive and will quickly die if kept in water below 70 degrees.
Not unlike other fish that have been introduced to Florida waters, the pacu can sometimes survive in south Florida water and occasionally you’ll hear about someone catching one that weighs 15-20 pounds.
The pacu is a member of the characin family, also known as tetras. Another close cousin is the silver dollar.
Many people purchase pacus without realizing how fast and how big they grow. They are one of the largest aquarium fish sold to the public, often with little to no warnings. Larger species often exceed two feet, with record-setting fish over three feet in length. These fish generally live for four to 20 years, depending on the species and the quality of care provided for them (larger varieties tend to live longer).
Years ago, when I lived in Jupiter, I raised six pacus in a 125-gallon aquarium until they reached about 10 inches in length. Like many people who attempted to raise these monster fish, I couldn’t afford to get an even larger aquarium, so I decided to let them go in my pond.
The pond was about a fifth of an acre and had a depth of about 10 feet. It was full of largemouth bass, but they had no interest in the pacu’s.
They grew fast and within six months they were all probably 16-20 inches in length. My pond was full of hydrilla, Kissimmee grass, pickerel weed, bullrushes and lily pads, so there was plenty for them to eat.
They always stayed together in a school, often just swimming along the surface, creating a wake similar to a small boat. And they loved bread.
Because I stocked the pond with too many largemouth bass, I would go to the grocery store and buy large bags of frozen smelt. I’d dump the fish into a five-gallon bucket and the bass would line up, like cordwood, waiting for me to toss the thawed-out smelt into the water. With the first handful, it was like a feeding frenzy. The water just exploded.
The pacus soon began to participate, even though they are not generally meat-eaters; like carp and goldfish, they too will not pass up an occasionally meaty meal. But what they were really looking for was bread.
After I fed the bass all the frozen smelt that I had, I’d toss old bread into the pond and the pacus would have their own feeding frenzy.
This went on for months until we had a major storm and the entire area that I lived in, Jupiter Farms, was under water. Other than the area within four feet of my house, everything was covered with two to three feet of water.
Days later, when the water receded, all my bass and pacus were gone.
I’ve since raised a few more pacus, recognizing how quickly they grow and allowing for that growth in larger aquariums.
George, a pacu I raised for a couple of years, was well over 15 pounds when I finally traded him to a guy who had a 500-gallon tank in Tampa.
But consider this a warning, although they look harmless enough in the small aquariums at the pet shop, don’t buy one unless you’re prepared to deal with their rapid growth and huge size.
Next week, I’ll be writing about red-belly piranhas.
Don Norton, is an aquarium hobbyist who raises a wide variety of tropical fish. He currently has about thirty aquariums, ranging in size from five gallons to 150 gallons. He has been an aquarist for the last 55 years, raising over 150 different varieties of fish.
