With an omnivorous diet like the Piranhas it can have a rapacious appetite, so any food that it comes across can be devoured, but what about larger crustaceans?

So, will Piranha eat crayfish? In short, yes they will eat Crayfish but there are some important nuances. Adult Piranha in the wild consider crustaceans in the wild, so Piranha will attack shrimps, prawns and crayfish. Crayfish will eat anything, and can often keep a tank clean. However, a decent sized crayfish will attack juvenile Piranha. Piranha are diurnal and crayfish are more active at night and can inflict either damage or a fatality on your fish. A good sized crayfish can decimate a tank full of small Piranha, so be careful putting these two species together.

What Are Crayfish

Crayfish, which can also be known as crawfish or crawdad, are crustaceans of the order decapoda, meaning having 10 legs, similar to the taxonomy of shrimp and prawns.

The northern hemisphere possesses the order Astacidae and the southern hemisphere where most Piranha reside , contains the order Parastacidae. Nearly all species are freshwater amd over half of the species live in the northern hemisphere.

Crayfish will have a conjoined head and thorax with a segmented body structure which are often dark brown, red, green or a sand colored yellow. They have a blunt head with eyes on movable stalks called compound eyes.

Primarily known for their thin but tough endoskeleton, but also for their from pair of legs being powerful pincers, much like a crab. Being a member of the decapoda order, they have 5 pairs of legs with which to move around.

An adult crayfish will range from 2.5 centimeters to 3.5 inches from most parts of the world, although the largest known crayfish is the Astacopsis gouldi from Tazmania, which can reach 16 inches and weigh 8 lbs.

Crayfish typically hide and conceal themselves in river vegetation, and are common to many lakes and streams in north America. They are nocturnal, and feed on snails, larvae, worms and other assorted food matter.

Although they are closely related to prawns and shrimps, they are different in a few areas, even though they are both decapoda crustaceans. 

Why Might Crayfish Be In The Tank

When keeping an aquarium, some people just like to add another species to compliment there preferred one. When doing this it seems sensible to add a species that performs a function of some kind.

Piranha are messy eaters, and you should clean the tank to keep the water clean, but keeping crayfish seems like a good idea. In the wild, their diet is just about anything that they come across. They will devour all types of food. Seems a perfect match for a Piranha, which spills its food everywhere.

Being omnivorous in nature, they will happily scour the bottom of the tank for bits of leftover fish, shrimp, fruits or vegetables that were missed by the Piranha. In fact a broad diet can keep them healthy, and some species can live to 20 years of age.

So keeping them in a Piranha tank can seem like a good idea, but no so fast…….for 2 very important reasons.

So Piranha Will Eat Crayfish Then

The Piranha in the wild have a varied diet. As soon as they hatch they mainly feed on plant matter, but as they mature, young Piranhas may eat copepods, crustaceans, and insects. 

The Native South American Crayfish is prevalent in southern Brazil, amongst other crustaceans.

Piranha will quite happily eat crayfish as a food source, so any in a tank could well become food for your fish.

But that is not quite as simple as it seems, because it is not quite so one sided, there is an important caveat.

Crayfish Are Not Defenseless

Unlike prawns and shrimps, which are most notably quite small, crayfish as a species are a bit bigger, but they have another distinction. Those claws are not for show, they are a defensive weapon, as well as a means of attack.

While there is no doubt that a fully grown adult Red-Bellied Piranha, especially a school could overpower a crayfish, Piranha have to get to adult size in the first place.

There are several reports where young or juvenile Piranha have been eaten by a large crayfish, at least one of the sizes of crayfish capable of pincering a small fish. There is considerable danger of losing your young Piranha if there is a sizeable crayfish in the tank. You may want them in there to clean away the detritus, but they could well inflict a fatality on your fish, or at least seriously injure them.

It should be noted that while Piranha are diurnal, crayfish are nocturnal. Essentially both Piranha and crayfish are active during different periods of the day. There is every chance that a decent sized crayfish could attack a juvenile Piranha while it is resting.

A 2.5 inch crayfish is perfectly capable of decimating a tank full of 1.5 inch Piranha.

Conclusion

If you plan to feed your Piranha crayfish, then be careful. Catching them from a nearby stream, and placing them in the tank could easily transfer disease. Piranha naturally eat crustaceans, so Piranha will feed on them.

The big proviso is that a large crayfish will quite happily remove juvenile Piranha from the tank. They operate at different times of the day, so a crayfish may catch a resting Piranha unaware, and the smaller the Piranha the greater the risk.

A large adult Piranha though, has little or no risk from any crayfish. Piranha bites can go through crabs, so the softer shells of crayfish pose no problem.

In summary, it is probably not a good idea to keep the species together, as the crayfish have pincers that could at least damage Piranha in any attack. There are easier options to feed them, and fish based food for Piranha should primarily concentrate on frozen  white fish.