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Pseudacanthicus Serratus (Mustang Cactus Pleco)

Pseudacanthicus serratus is commonly known as Mustang cactus pleco. It is a tropical freshwater fish.

Pseudacanthicus Serratus

Cactus Pleco is also known as suckermouth catfish and belongs to the armored catfish family that is named for the longitudinal rows of armor-like scutes that cover the upper parts of the head and body (the lower surface of the head and abdomen is naked soft skin).

Their whole body is covered with pointy spikes, which can cause bleeding injuries when touched with bare hands. 

Pseudacanthicus serratus has rather larger fins, like many other Pseudacanthicus spp. has. The overall body coloration of adult P. serratus is dark black while juvenile plecos show bright white spots. 

Although the white spots disappear when they become adults, in rare cases, adult specimens can show small white spots. They are popular in the aquarium trade as bottom cleaners.

Mustang cactus plecos belong to the family of Loricariidae. They are the largest family of catfish with 92 genera and over 680 species.

The members of this family originate from freshwater habitats of Panama, Costa Rica, Guyana, and tropical and subtropical South America.

Although the native place of P.serratus is the region around Paramaribo, Suriname, they distribute in drainages of French Guiana and Suriname.

They live in the deep and rocky zones of the main riverbed according to Boni fishermen in Guiana. Despite its size, it is not consumed as food by native populations since it has a reputation for being dirty and sticky.

Mustang Plecos are not considered endangered fish on IUCN Red List and are often caught for the aquarium trade.

However, some of the species in the genus are threatened by mining, deforestation, and especially the building of dams. 

How big do Pseudacanthicus serratus get?

They are large freshwater creatures and their average length fluctuates between 35-38 cm. However, the maximum length reported for this species was 40 cm.

Their size can be influenced by a number of factors while genetics and the level of care you provide are the main contributors.

Is Pseudacanthicus serratus aggressive?

Like many members of loricariid daily, they are quite aggressive. They can be aggressive toward each other and other loricariid species.

You need to arrange their tank to reduce their anger as their fights may end up with serious damage as they have sharp spikes covering their bodies.

Pseudacanthicus serratus behavior

These species of Plecos are quite aggressive. They prefer to spend the most time near the bottom of the tank. Mustang cactus plecos prefer to live alone and are not very social fish.

They tend to be more active at night and hence, they are categorized as nocturnal animals. This fsh often hide in their caves or behind tank decorations such as driftwood, when they feel threatened.

They can be very aggressive and territorial when it comes to their favorite hiding spots.

How long do Pseudacanthicus serratus live?

They are quite hard to fish when they are established in your aquarium.

Like many of their close relatives, Mustang Cactus plecos have quite a long lifespan which is close to 12 years. You can enjoy their company for approximately a decade if you treat them in the right way.

However, like many aquarium fish, their lifespan can vary depending on several factors. Bad water conditions, poor quality food and stress from other tank mates can shorten their lifespan although they are considered hardy fish in the trade.

One look Care guide

Scientific namePseudacanthicus serratus
Common nameMustang cactus pleco,Black pleco
Care levelEasy
Native toSuriname  to  Guyana
( Paramaribo ~ Maroni River)
Type Freshwater 
Color Black Juveniles have white dots 
Tank size90 gallon
Prefered temperature76-82F
Other water parameters (ammonia ,ect)Ammonia:              0ppm
Nitrite:                    0ppm
Nitrate:                  <30ppm
Prefered salinityNone
Size 35 -40 cm
Growth rateRapid 
Temperament Aggressive
Recommended tank matesOscar fish
Green Terror Cichlid
Keyhole Cichli
Chocalate Cichlid
Cory catfish
Ember tetra 
Prefered foodPrawns
Chopped mussel
Other meaty commercial foods
Feeding frequencyOnce a day for adults Few times a day for juveniles 
BreedingEgg layers 

Pseudacanthicus serratus care

Pseudacanthicus serratus size

They are quite large fish and can grow up to 40 cm while their average length varies between 35-38 cm.

Pseudacanthicus serratus tank size

As mentioned before, these fish get huge and need a lot of space when they grow out. Even though it seems a bit inactive during the daytime, this fish swims a lot during the night. 

A single specimen needs 90 gallons, at least 100 cm (40 inches) in length and 40 to 50 cm (15 to 20 inches) in depth. The height is not that important because plecos are mostly bottom-oriented.

 If you are planning to keep two or more, it is advised to keep them in a tank 150 gallons or larger to avoid conflicts.

How many Pseudacanthicus serratus should be kept together?

Although they are quite aggressive, P. serratus can be together with the same species and other pleco species.

They are aggressive and territorial when someone tries to conquer their hiding places. Therefore, if you plan to keep two or more plecos together, you need to adjust your aquarium to fulfill their requirements.

You should structure well and provide substantial space and several hiding places to avoid territorial conflicts.

Further, as they are large carnivores they produce a massive load of biomass. Therefore, you need to install a big and efficient filter system 

Tank setup

They are quite territorial and try to hide and stay near the bottom. Therefore, you need to provide them with good hiding places such as big caves, driftwood and big rocks.

They enjoy digging the substrate and you need to install every decoration in a way that the P. serratus can’t toss it over or falls when being dug under. 

The substrate should be sand or gravel which makes them easier to dig. 

You do not need to bother to keep plants in your aquarium as they don’t prefer plants. Since plants are supplemental oxygen providers in an aquarium, install a second pump or air pump to increase the level of oxygen in the water if you are not going to keep plants in your aquarium. 

They are shy fish and are nocturnal. Therefore, dimmed light is recommended and it helps to see this shy fish more often over the day. 

Although they are bottom dwellers, it is important to place a  good lid on the aquarium, since they sometimes push themselves far above the water surface.

Actually, they tend to jump because of their uncalm behavior caused by gill worms. You need to pay attention if they show uncalm behavior such as trying to jump over the tank, swim fast, or reach for air outside of the water. 

 Further, long sight lines can promote aggression. Placing structures at different distances from the front glass is an effective solution.

More on, they are high waste creators and install a good filter system. 

Water quality condition

They are tropical freshwater fish and prefer warm water. The aquarium water should have a temperature of 26 – 31 °C. The aquarium water should be neutral to slightly acidic.

These carnivores produce a lot of ammonia, which can be lethal in high doses. Therefore, as mentioned before, provide good ventilation with an air pump and good filtration. The recommended water parameters are listed below. 

Ammonia: 0 ppm

Nitrite: 0 ppm

Nitrate: <30ppm

pH : 6 – 7.5

Pseudacanthicus serratus breeding 

Pseudacanthicus serratus male or female identification

P. Serratus shows sexual dimorphism and it is possible to distinguish the genders when they reach about 15 cm (6 inches).

Male of this species have longer pectoral and ventral fins, and their pectoral spines are thicker than those of the females.

Further, the heads of females are more pointed while the heads of males look bulky and chiseled. 

Pseudacanthicus serratus breeding

These fish are not bred for a long time as people keep only one specimen as they are large and territorial fish.

Also, they are troublesome when you are going to catch them to clean the tank or for transport to another place because of their sharp spines. Although there is a rumor that they cannot be bred in captivity, actually it is not very hard. 

It is better to keep your chosen pair in a separate tank, as there are many advantages to it. The advantages are,

  1. They don’t waste their energy in territorial fights with other fish
  2. No fight for food and getting enough nutrition which is vital for successful breeding 
  3. You can adjust the water parameters according to their needs
  4. Juveniles will not be eaten by predators.

Make sure your fish get proper nutrition as if they don’t get good protein-rich food, the female is not able to develop eggs.

It is important to feed them with frozen food and meaty tablets other than the vegetables and algae wafers during their breeding season. 

You can know whether the female is pregnant by observing its belly. The belly of an egg-bearing female will be much wider, and the male will look a lot more slender in comparison.

How to stimulate breeding

You can stimulate breeding through water changes. They breed during the rainy season in their natural environment.

The water should be neutral to slightly acidic. Keep the water temperature 27° to 32°C (80° to 90°F). It is better if you can put clean rainwater into the breeding tank.

Further, they need a cave to complete the breeding process. According to the research, you don’t need to bother about the color of the cave, but the size and the interior surface of the cave.

The interior surface of the cave should be rough to provide a good grip for the clutch. It should be quite a large cave, about 5 cm (2 inches) longer than the male’s total length and wide enough for the male to get in with both pectoral fins half-extended.

Breeding act

When the breeding starts, the male stays in the cave and the female tries to get into the cave. This is quite fascinating to see and it can take a few hours to a few days for females to enter the cave of the male.

Somehow, the female has to be in front of the male to lay her eggs along the top of the cave. After laying eggs the female leaves the cave.

The male fertilizes them just after the female lays eggs on the surface. After this process, the male stays in the cave and starts fanning with his fins. It helps to oxygenate the cave and keeps the eggs alive.

Depending on the temperature, they hatch after six to seven days.

How many babies does Pseudacanthicus serratus have?

Adult females can produce huge masses of eggs and potential juveniles.

It is reported the female can lay 500 eggs at a time. However, raising so many young fish can cause problems considering the space that is needed.

Pseudacanthicus serratus fry care

After hatching, larvae appear and use their toll sack for approximately five days.

During this time, the male takes care of them and does not release them from the cave. Afterward, the juveniles spread into the tank and grow up rapidly.

Alternatively, you can take the cave outside the water and move the eggs or larvae into another tank.

This is more advantageous as you can feed them better a few times a day in this special tank. P.serratus grows rapidly and during the first few months becomes more stable.

The breeders face difficulties at 3 cm (1 inch) in size of juveniles as they often start dying at this age.

The reason is young plecos don’t have enough space to hide from each other as the tanks are overcrowded with youngsters. They get stressed due to limited space and other parameters such as oxygen. 

Another factor for the high mortality is a high concentration of bacteria. The bacteria concentration tends to be very high in small tanks with so many fish.

Therefore, keep in mind to have a big aquarium if you are going to breed them in captivity. Try to keep the water parameters in good condition and feed them regularly. Despite, the above issue, raising the juvenile plecos is easy and they will grow up quickly.

You can feed them with brine shrimp or other commercial food items according to their size.

Feeding behavior of Pseudacanthicus serratus 

What do they eat

They are carnivores and are not predators. In the wild, they feed on snails, insects, dead fish and comparable organic stuff.

In the aquarium, they can be fed with prawns, chopped mussels and other meaty commercial foods. Also, you need to provide them with vegan food too to get balanced diet.

However, as they are bottom dwellers, sinking pellets and wafers are made especially for them. Make sure to feed them with enough food, which they can eat within two or three minutes, otherwise, the water can be spoiled by the remaining food items. 

How often should you feed

Juveniles should be fed several times a day. It is enough to feed the adults once per day.

When should you feed (time of the day)

They are nocturnal animals and mostly active at night. Therefore, it is better to feed them at night or when the aquarium is dark.

How long they can go without food

You don’t need to feed them necessarily, as they are eating algae that are growing in your tank. However, eating only vegan foods make them weak and affect their reproductive ability too.  

What fish can live with Pseudacanthicus serratus?

They are aggressive towards most bottom-dwelling tank mates of their species and other species.

However, they actually work quite well with most omnivores or vegetarian plecos. If you are planning to keep them with more plecos you should have a large aquarium. 

Generally, they do not harm or harass other species. As they are bottom dwellers you can accommodate typically swim in at the top, or middle of the tank.

Oscar fish, Green Terror Cichlid, Keyhole Cichlid, Chocolate Cichlid, Cory catfish and Ember tetra are possible tank mates for them. However, despite their defensive protection can be bullied by faster-moving fish of similar size.

Is Pseudacanthicus serratus aggressive?

Yes, they are aggressive toward the same species and most other bottom-dwelling species. 

Can Pseudacanthicus serratus live in a pond?

They can thrive in ponds. Actually, when they are fully grown up they need a huge space due to their size and experts recommend putting them in ponds. They are generally hardy species and can thrive in many hard conditions. 

Credit to : Jason’s Plecos & Cichlids LLC
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About Dr.Chamika

Hello, I'm Dr. Chamika. I am a Researcher in Water quality, Aquatic organisms, and Environmental chemistry. I am a passionate fish keeper, with10 years of experience. My mission is to help other aquarists experience the joy of fish keeping.