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How Many Bristlenose Pleco Can Live In A 20 Gallon Tank? Fact & FAQ

Lindsey Stanton Profile Picture

By Lindsey Stanton

bristlenosed pleco

There are a few different kinds of bristlenose plecos out there, and they’re all very beautiful because they have those eye-catching bristles. Although these fish can look a bit intimidating, they’re actually very peaceful.

Now, you might be wondering, how many bristlenose plecos in a 20-gallon tank can I fit comfortably? Each Bristlenose Pleco requires 10 gallons of space, so you can house 2 in a 20-gallon tank. Remember to not keep more than 1 male in the same tank.

Let’s take a closer look and talk about everything you need to know to keep these awesome fish happy and healthy.

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How Many Bristlenose Plecos Should I Get?

Bristlenose plecos are very peaceful creatures, and although they are not technically schooling fish, they do prefer to have some tank mates.

What is important to note is that male bristlenose plecos can be quite aggressive towards one another, especially during mating season. Therefore, it is not recommended to keep more than a single male in the same tank. However, a male with a female or two should be fine. That said, small and peaceful fish tend to make for the best bristlenose pleco tank mates.

Minimum Tank Size for Bristlenose Plecos

Following the general of thumb rule, each inch of fish should have a gallon of water. Bristlenose plecos usually do not grow longer than 5 inches. This would mean that a single bristlenose pleco would require 5 gallons of tank space, but do keep in mind that this is a bare minimum.

We like to double this rule, mainly because some fish do need a bit more room than others, so we would say that each inch of fish needs 2 gallons of water. This means that a 5-inch bristlenose pleco would need 10 gallons of tank space to be happy and stress free.

Bristlenose Plecos Housing Requirements

Image Credit: Petr Kratochvil, Pixabay

Before you go off and get yourself a bristlenose pleco, there are a few things that you need to know about them in terms of their housing requirements, so let’s take a closer look.

Water Temperature

Bristlenose plecos are warm water fish which do not handle cold water very well. They require their water to be between 73 and 82 degrees Fahrenheit, or between 23 and 27 degrees Celsius.

For most people, this will mean that you will need an aquarium heater to get the water up to the ideal temperature, as about 76 or 77 degrees Fahrenheit is the best possible temperature.

Water Hardness

Bristlenose plecos are one of the few aquarium fish out there which do actually prefer their water to be medium-hard, whereas most other fish like their water to be on the softer side of things. Bristlenose plecos prefer their water to have a hardness level between 20 and 25 dGH, which is actually quite hard.

Now, if you are using tap water, chances are that your water is hard enough for them, although you should get a testing kit and, if necessary, water conditioner that can add dissolved minerals into the water.

Water pH

One thing which bristlenose plecos are not picky about is the pH level or acidity of the water. A pH level between 5.8 and 7.8 is fine for these fish.

This means that they do fine in acidic, neutral, and slightly alkaline water as well. Generally speaking, if you are using normal water, you should not have to manually alter the pH on your own.

Filtration & Aeration

under water bubbles
Image Credit: Tracey Jones Photography, Shutterstock

Bristlenose plecos prefer their water to be very clean and they don’t like strong currents. Therefore, you should aim to get a trickle or canister filter that can process two to three times the total water volume in the tank per hour. Ideally, a 20-gallon bristlenose pleco tank should have a filter that engages in all three major types of filtration, which includes mechanical, biological, and chemical filtration, and that can process 50 to 60 gallons of water per hour.

Do make sure to get a filter with an adjustable flow rate, so you can keep the current low. Also, due to the fact that these fish prefer very well-aerated water, you will definitely want to get an air stone and/or an air pump.


Bristlenose plecos also aren’t overly picky about their lighting. They don’t need a really bright environment, as they are pure bottom dwellers, and water at the bottom can often be quite dark. Therefore, a simple aquarium light that can mimic normal daylight will do just fine here.


Bristlenose plecos are bottom feeders and often like to rummage around in the substrate. Therefore, you should aim for a really fine and smooth type of aquarium gravel, and you may also go with fine grain aquarium sand, although fine grain gravel is best. You will want to provide them with between 1 and 2 inches of substrate.


A green beautiful lush planted tropical freshwater aquarium with fishes
Image Credit: Bukhta Yurii, Shutterstock

These fish are nocturnal, they like to hide, and they really like their privacy. Therefore, you should aim to provide your bristlenose plecos with plenty of plants. They prefer very heavily vegetated tanks with plenty of big leaves and grass-type plants. Anything they can swim through, explore, and get some cover under will do fine. Hornwort and Java moss are both great options to consider.

Rocks & Deco

You should add plenty of rocks, hollow caves, and hollow driftwood to your bristlenose pleco tank. Anything that they can swim into and hide in, particularly during the day, is preferred.

Tank Mates

The bristles on these fish will provide them with a good amount of protection from aggressive fish, but that said, whether smaller or larger, keeping bristlenose plecos with aggressive fish is not recommended.

Fish may be smaller or larger than plecos, but they should not be aggressive, as this will end up causing lots of stress. Platies, neon tetras, guppies, and other such fish make for good bristlenose pleco tank mates.

Image Credit: Piqsels

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How Many Bristlenose Plecos in a 55 Gallon Tank?

Based on our own rule of 2 gallons of water per inch of fish, and seeing as each pleco can grow to around 5 inches in length, we would recommend having no more than five bristlenose plecos in a 55-gallon tank. Remember that males can get aggressive with each other, so tank size is extremely important.

Can You Keep 2 Bristlenose Plecos Together?

Male and female bristlenose plecos can be kept together with no problem. That said, keeping more than a single male in the same tank is a risky move.

Are Bristlenose Plecos Aggressive?

Bristlenose plecos are generally solitary and peaceful bottom feeders that are not aggressive towards other fish. They will only become aggressive towards other bristlenose pleco males, particularly during mating season.

Do Bristlenose Plecos eat other fish?

No, they generally won’t attack or eat other fish. However, they have been known to eat fish that are already dead.

Albino Bristlenose Plecostomus
Image Credit: Ken Lord, Wikimedia Commons CC 2.0 Generic

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As you can see, in large, these bristle nose plecos are quite easy to care for. Just give them a fairly large tank with good aeration and filtration, keep it warm, and add plenty of plants and hiding spaces. These bottom-feeding fish make for great cleaners that will eat algae out of existence!

Featured Image Credit: TTONN, Shutterstock

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