The Piranha Page

Piranhas! 

By Christina Obrecht, , 2011

General info/history:

Piranhas are a member of the large family of more than 1,200 species of Characidae. They are a freshwater fish that inhabits South American rivers, such as the Orinoco, Guyana’s, the Paraguay-Parana, and the Sao Francisco river systems. Some species have a broad distribution; others are more limited.

Piranhas belong to the subfamily Serrasalminae - which also include their cousins the pacus. The subfamily name means “saw, sawed, or serrated”. Serra meaning saw, Salmus meaning salmon. Only four genera (Pristobrycon, Pygocentrus, Pygopristis, and Serrasalmidae) are the true piranhas. The total number of piranha species is unknown; there is an estimated 30-60 species, with new species being found quite frequently. All fish in the subfamily serrasalmus have a streamlined body for faster swimming. Serrasalmidae is divided in separate genera: pygocentrus, serrasalmus, pristobrycon, pygopristis, catoprion, metynnis, colossoma, and a few others. The piranhas most commonly kept as pets are from the genus serrasalmus and pygocentrus. The most infamous piranha kept is the red-bellied piranha; “Pygocentrus Nattereri.” The pygocentrus group of piranha have a convex head, while the serrasalmus piranha have a concave head.

Piranhas have been evolving for about 15 million years; while some subfamilies of piranha have been in existence for over 25 million years. The piranhas name is inspired by their teeth; the word piranha comes from the Portuguese “piro” for fish, and “sainha” for tooth. They are also known as “caribe” which is derived from the Carib, an indigenous group for which the Caribbean Sea was named. Roughly 20 of the piranha species are omnivorous, feeding on seeds and meat. Unfortunately, these fish have a bad reputation as ferocious killing machines. Piranhas in the wild mainly eat injured or dead fish as far as “meat” goes; however they do occasionally eat other small mammals such, as birds that fall into the water, and larger animals that were attacked, are weakened, sick or injured. If you were to sit in a pool full of piranha, they would not attack as many people think they would. Much like vultures, piranhas are the health police of their habitat as they are mainly scavengers. They are a shy species of fish, and humans are not on their food list! Piranhas will also supplement their diet with fruits, nuts, and seeds. They locate their prey by scent or motion using a set of sensors down the sides of their bodies called the lateral line. All piranhas have have a single row of sharp teeth in both jaws; usually tightly packed and inter locking which are used for rapid puncture and shearing. Piranhas not only “school” for protection, they also “school” for cooperative hunting. Piranha sizes range from 5.5 inches to 17 inches.

All piranha species have a powerful, high, thick but laterally compressed body shape, with keel-like edges running over the upper part of the body from head to dorsal fin, and on the lower body running over the belly. Their streamlined bodies make them very fast and agile swimmers. Unlike many fish species, piranha’s have a small adipose fin between tail and dorsal fin. This feature is characteristic for the Characin-family. Their predatory lifestyle is reflected by large eyes and a large nose with big nostrils to maximize the water inflow. They have a very acute sense of smell: in their natural habitat, murky rivers in South America, even more darkened by overhanging vegetation, scent is their main way of tracking their prey.

While piranhas in the wild and in captivity live in shoals, there will always be one or two dominant animals. The leader of the pack will generally be the largest, most aggressive, and bold piranha. The alpha fish will usually own and guard the best spots in the tank and will be the first one up for feeding. Piranhas always live in a state of fear and mutual mistrust. To survive, the fish must always know where the others are, what their states of mind are, and how they might act the next moment. Do not be surprised to see parts of their fins missing or fins missing all together, as this is common in shoals. Most piranhas are less skittish and shy when they live in a tank with plenty of hiding spots and dimmed lights. It makes them feel more secure, and will also let them be more active and behave in a more natural way.

While I know a lot of piranha keepers love to feed live food to their piranhas, I advise against it! Most owners feed live just for the sake of watching the piranha tear the live food to pieces. Live food can introduce diseases, and goldfish contain a growth-inhibiting hormone which in turn will affect them. You can feed your piranha lean meat, such as beef heart - OCCASIONALY, fresh fish fillets, invertebrates such as shrimp, and crab, prawns, mussels, squid, whitebait, and cockles. Too much meat in their diet can lead to liver failure, as they do not have the physiology to effectively digest animal protein. Feeding of oily fish, such as salmon and mackerel, is also not recommended as this can pollute the water. Dried foods, such as cichlid pellets are a good choice; as it is a more balanced and contains vitamins and other nutrients. A varied diet is the best; if only fed one type of food, you may have a problem getting them to eat new foods. We feed our piranhas cichlid pellets, brine shrimp, occasional chicken, boiled peas, and krill. Remember, piranhas are programmed to survive; this means they will adapt to the available food sources and will not let themselves starve.

Extensive filtration system is a must with piranhas, as they will generate a lot of waste due to their diet. Internal filters are not really suitable as they do not have an adequate capacity to deal with the waste levels. I suggest using an external filter if not two, depending on the size of your tank as well as how many piranha you have. We use an external canister filter that is for twice the amount per gallon in the tank. For example, if you have a 125 gallon tank buy a filter that can clean up to 300 gallons, or if you have a 55 gallon tank, use a filter that can clean up to 125 gallons, etc. You can also use a power head or water pump to create a strong water flow; which forces the fish to keep active by swimming against the current. This can also boost their metabolism, ensuring they will readily eat. You should also so a 20% water change weekly.

I would not recommend any bubblers, as this may prove to just be a waste of money. Our piranha are constantly serrating the tubes to the bubbler.

Ideal pH for piranhas would be between 6.0-7.0 - we keep ours at 7.0 with an ideal temperature of 79 degrees. Make sure the water hardness level is not more than 2.0. Nitrates should be kept as low as possible. There are plenty of water testers in the stores you can buy to keep an eye on ammonia, nitrates, nitrites, pH, and water hardness.

As mentioned earlier, use dimmed or reduced lighting for your piranhas. This will also encourage them to emerge from their hiding places and allow them to feel more secure. Remember in the wild, these fish live in the rivers that are highly crowded by vegetation. This may prove difficult to those owners who may want to keep live plants in their aquarium, as many plants need full spectrum lighting to thrive; however there are a few plant species you can use that grow well in dim light - anubias, and cryptocoryne are two good examples. Bogwood, branches, and rockwork are great and natural décor for piranhas, just be careful if you have heavy rocks or décor that they are secured as these are powerful fish and they could knock over the decorations into the glass and break the aquarium. The more hiding spots, the more likely the fish will feel secure enough to venture out into the open water.