How To Care For A Bristlenose Pleco Fish: A Complete Fact Sheet, Breeding, Behavior, and Care Guide

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The first time I saw a Bristlenose Pleco, I wondered if they looked the same during the dinosaur era. While not a brightly colored or fast moving aquarium fish, the Bristlenose Pleco has fascinating physical characteristics and mannerisms. 

Overall, this is a slim bodied fish that tends to grow sideways instead of tall.

There are several color variations in Bristlenose Plecos, but most are a darkish grey-green with lighter spots. There are also black plecos with white polka dots and albino bristlenose fish. 

bristlenose pleco fish on the bottom of a tank

Quick Intro to Bristlenose Plecos

FamilyLoricariidae
Scientific NameAncistrus Cirrhosus
Other NamesSuckerfish, Brushmouth Pleco, Bushynose Catfish, Bushy Nose Pleco, Bristlenose Catfish
Care LevelEasy

Pleco’s pectoral and anal fins extend horizontally from the fish’s body instead of vertically.

From an anatomy point of view, this fin configuration makes perfect sense because plecos have a sucker mouth (hence their name) located on the underside of their body.

The horizontal fin configuration makes it easy for them to latch onto plants and algae without losing fin mobility.

As for gender differences, males are larger and have pronounced spikes on their head and around their mouths. Females are smaller and have spikes around their mouth, but not on their head. 

Both genders move slowly around the bottom of the tank. You may also see them attach themselves via their mouth to the wall of the aquarium.

They will also attach to just about anything else in the tank, including fish that cannot escape from them. 

Since Bristlenose Plecos love to dine on algae, many aquarists use them for this purpose.

Unfortunately, I have also seen them snacking on sick or dying fish in the pet stores many times.

Plecos also produce a lot of waste, which means the consumed algae turns right back into ammonia.

I like to put Plecos in low shallow tanks landscaped to look like dinosaur era volcanoes, or dense jungles. In a tank by themselves, Bristlenose Plecos are absolutely fascinating freshwater fish to watch and a joy to take care of. 

Natural Habitat, Identification, and Where to Buy

Bristlenose Plecos originate in the Amazon River Basin and its tributaries. 

The water tends to be acidic and tannin rich.

bristlenose pleco front facing

When you visit the pet store, you may have a hard time telling the difference between Bristlenose Plecos and Common Plecos. Both look similar in coloration when they are young. 

Common Plecos, however, will grow rapidly and are more likely to attack other fish in the tank. By the time you realize your mistake, it will be too late. This is why I find it best to buy Bristlenose Plecos online.

Here are a few options I recommend on Amazon.com:

While Common Plecos are also fascinating aquatic creatures, this article is dedicated to Bristlenose Plecos. 

Optimal Water Conditions for Bristlenose Plecos

Water Temperature75 – 82 Degrees Fahrenheit
Water Flow RateRapid with strong filtering
pH Levels5 – 7.5 (prefers acidic but can adapt to alkaline water)
Hardness2-10 GH
Aquarium Salt RecommendationsAvoid using aquarium salt as it will kill plecos and other members of the catfish family.
Tannin RecommendationsPreferred for Plecos
Other Water Chemistry NeedsTry to keep the carbonate levels high to avoid pH swings in tanks with fry or young plecos.

Tank Setup

Minimum Tank Size30 Gallons
Optimal Tank Size40 Gallon, Long Freshwater Aquarium, or 50+ Gallons
Optimal Tank ShapeLong and low
Recommended Filter TypeCanister with ammonia, nitrate, and nitrite absorbing media
Extra Air Flow and and How to Provide ItMany plecos originate in parts of the Amazon where the water moves very fast. To provide extra air, I prefer to use a bubble curtain and install it just above the gravel line.

Even though they aren’t very big, the bioload from Bristlenose Plecos is much larger than from other fish their size.

If you have plecos in a newly cycled tank, be sure to test daily for ammonia, nitrates, and nitrites.

Once the tank is a year old, you can scale back to once a week, and then every two weeks.

Creating the Landscape 

Overall, Bristlenose Plecos are happiest when they have plenty of driftwood and cave structures to hide under.

Best PlantsFloating live plants that will block out most light going into the tank. Fast growing low light plants will also be useful for providing hiding places and absorbing nitrates from the water.
Best LightingLow light. Be sure to turn the lights off each night because Bristlenose Plecos are nocturnal. If the tank is not dark, they will not eat.
Best DecorationsCaves and anything they can hide under. A piece of driftwood is also very useful because plecos will snack on it and gain some much needed fiber.
Decorations to AvoidAnything plastic that has sharp seams. I also don’t recommend toys that open and close. Plecos are thin bodied and small enough to get trapped in air powered seashells and other toys that move in a similar fashion.

Physiological Considerations

Maximum Size6 inches
Rate of GrowthReaches adult size in 2 years, but grows fastest during first 6 months of life.
Life SpanOver 5 years
TemperamentPeaceful when young, but can become aggressive over mates, territory, and food.
Preferred Tank RegionBottom
Scale ThicknessBristlenose Plecos do not have scales. They have exoskeletons that do not protect them from many antibiotics, salt, and many other chemicals.
Swimbladder ConsiderationsThese fish are accustomed to staying in the bottom of the tank. They can still have a hard time regulating their position in the tank if they do not have sufficient fiber to push out air bubbles. Feed them canned peas 1 – 2 times a week to avoid this problem.
Fin Shape ConsiderationsUnless you buy the veil tail Bristlenose plecos, you will find their fins are very compact and strong. They are strong, but not fast swimmers.

Society

Psychology wise, both males and females are peaceful fish as juveniles. They will not fight among themselves or with other fish.

Plecos usually do not form schools or interact with other tank mates.

Females will continue to be fairly peaceful even after they reach puberty and begin to lay eggs. You can keep as many as 3 or 4 females to a tank provided it can handle the bioload.

Males, on the other hand, will become aggressive at puberty. If there is another male in the tank, they can and will fight to the death.

Usually, males will not be aggressive towards females of their own species. Once a female lays eggs in a male’s cave, however, he will chase her out and devote his time to taking care of the eggs.

It is best to keep one male to 2 – 4 females per tank.

When Bristlenose Plecos become aggressive, they will usually charge at other fish. Their bony exoskeletons and extensions can do quite a bit of damage to other fish.

Here are some things you can do if you see plecos chasing other fish in the tank:

  • See if the fish they are chasing is sick or dieing. 
  • Chasing other fish may be a sign of dietary imbalance. You can try adding blood worms, black worms, and different vegetables to see if it helps.
  • Increase light during the day hours. This will cause plecos to hide and sleep. Unfortunately, this won’t be of help if the pleco decides to be aggressive at night.
  • Put up a partition for isolation
  • Place the aggressive pleco in a tank by itself.

Gender, Breeding, and Reproductive Considerations

 As long as the water is in good condition, and the fish are well fed, you can rest assured that female Bristlenose Plecos will lay eggs, and males will fertilize them.

However, ensuring they reach maturity can be difficult. You will need to plan ahead to ensure the best possible outcome.

For the most part, fish you purchase at the pet store are healthy enough for a home environment. But, these fish are not the best representatives of their species. Even if they do produce offspring, they may not be as healthy as the parent fish. 

Since Plecos and other egg layers can produce hundreds of viable eggs, you will also need to figure out how you will house them all.

As a home aquarist, or someone new to fishkeeping, this isn’t something to try “just for fun”.

Here are some important things to consider for breeding:

  • Once a male fertilizes eggs, he will become territorial and aggressive. Other fish in the tank, however, will do everything they can to consume both the fry and the eggs. 
  • Unlike tiger barbs, tetras, and goldfish that consume their own eggs, male Plecos will fight to exhaustion and death to defend eggs and fry. If you do not want a lot of injured fish in the community tank, it’s simply not a good idea to keep male and female plecos together.
  • Even if you put a male and female pair in a breeding tank, you will still have to figure out what to do with all the fry that survive. Decades ago, you might have been able to sell them around the neighborhood or to the local pet store. 
  • Today, there are very few, if any non-franchise pet stores that will buy your fish. It is also illegal in many areas to dump tropical fish into freshwater rivers, waterways, and other areas. This means you will either have to start dozens of new tanks or euthanize the fish.

If you have a male and female Bristlenose Pleco or want to try breeding them, the male will do most of the work for you. He will take care of the fertilized eggs and guard the fry until they are free swimming. 

You can tell when plecos are about to mate because the females will become heavier in the midsection as the eggs mature. Males will clear out a cave and stay in it to attract the female. 

After fertilization, the eggs will hatch in 6 – 10 days, and then become free swimming in about 4 days. You can feed the fry infusorians, spirulina, or pre-manufactured fry food. They will also begin sucking at the walls of the tank and consume any algae they can find.

Nutritional Needs

In the wild, Bristlenose Plecos consume algae, driftwood, the remains of dead fish, and plants. While they are considered primarily herbivores, they still need some animal flesh to replicate a natural diet. 

It is also very important to make sure the food sinks to the bottom of the tank or they will never find it.

You should also feed Plecos after dark. If the aquarium is too brightly lit, they will never come out to eat.

Best Sustenance Food TypeSinking pellets or sinking algae wafers
Additional Foods for Optimal HealthPlecos also need vegetables for fiber and additional nutrients. Cucumbers, lettuce, zucchini, and spinach all work well.
Special Foods and Considerations for Best Color and GrowthBloodworms and blackworms will also help round out a Pleco’s diet.
When and How Often to Feed Fish Based on Life CycleFeed Plecos of all ages just once after dark. During that time, drop in either sinking algae pellets or some vegetables. You can alternate days on the wafers and vegetables.

After feeding Plecos vegetables, be sure to pick up any left overs the next morning. Vegetables will rot very quickly in the tank and cause ammonia surges. 

Once a week drop in some frozen or freeze dried blood worms. If you have egg-heavy females in the tank, you might want to add some extra vegetables and blood worms. 

Finicky Fish Management – Unless the fish is coming down with Ich (some fish will eat more), it is very likely that lack of appetite is caused by illness or a water chemistry problem. 

Start off by making sure the water chemistry is correct, and there are no toxins in the tank. If you suspect air freshener or other contamination, do a 30% water change and add bubble up filters filled with activated carbon to the tank. Use one filter to every 10 gallons of water. 

This is also a good time to begin feeding medicated wafers. Make sure the wafers are safe for Plecos and do not contain salt.

As long as you can keep the fish eating, it will have a chance to fight off any infections that are trying to take hold.

If the fish is not sick, try feeding different vegetables, or change to a different brand of food. Fish can and do get bored if you don’t give them some variety in their diet!

Common Diseases and How to Avoid and Treat Them

Insofar as common tropical fish diseases, Plecos are most susceptible to Ich, Hexamita (Hole-in-Head), body fungus, Pop Eye, Dropsy, and Fin Rot.

While there aren’t any specific bacterial, fungal, or viral infections unique to this species of fish, they suffer most from malnutrition. Many hobbyists think the fish can get by on algae and never need additional food. 

They need fiber in their diet to aid digestion, and also meat and vegetables for additional nutrients and minerals.

Sinking algae wafers will help, however for long life and good health, these fish also need additional foods.

Best AntibioticsIf your Plecos shows signs of a common infection, you can use antibiotics commonly used for that condition. Since different diseases are only susceptible to certain antibiotics, you may need to keep several different kinds onhand.
Treatments to AvoidNever use medications that have salt in them. You should also avoid antibiotics that are dangerous to catfish and other fish that do not have scales.
Food Recommendations When SickMedicated sinking fish food. Increase vegetables and also try some frozen bloodworms.
Hospital Tank or Isolation Within the Community Tank SpecificsWhen one fish in a tank gets sick, the rest usually follow suit. As such, there is not much point to putting your Pleco in a hospital tank.

If you notice other fish nipping at the Pleco or disturbing it, a temporary partition might be useful. Just make sure the Pleco’s partition has a nice cave to hide in.

5 More Important Things to Know About Bristlenose Plecos

  1. When Plecos go to the top of the tank more than once a day, there may not be enough oxygen in the tank.
  2. Adult Plecos are less sensitive to pH changes than fry and young fish.
  3. If Plecos eat during the day, they may be coming down with an illness
  4. To watch plecos moving around during day hours, keep lights low or off in the aquarium. 
  5. Plecos can sit perfectly still for hours on end and will not move even if food passes right in front of them.

Bristlenose Plecos are an easy, enjoyable fish to take care of for beginning and advanced fish keepers.

As long as you meet a few basic needs in terms of diet and filtration, they will help keep your tanks clean of algae.

They can also offer a fascinating counterpoint visually to more brightly colored fish in your home aquarium. 

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