How Big Do Plecos Get? 6 Common Pleco Sizes by Age

Plecostomus or plecos are suckermouth catfish that thrive in fresh and brackish waters. Interestingly, they are also called the “janitor fish” because of their ability to clean tank algae. If you’re a starting aquarist, one question you may have is, “How big do plecos get?” 

Plecos grow up to 18 to 20 inches (45.72 to 50.8 cm), depending on the species you have. However, note that some species grow only up to 1.5 inches (3.81 cm). Tank size, diet, and the environment will determine how big the pleco fish gets.

In this article, we’ll get down to intricate details of pleco size, even by age. Keep reading to get the details.

How Big Do Plecos Get? Common Pleco Sizes at Different Ages

The table below illustrates the common pleco sizes by age:

Beyond tank size, diet, and water conditions, the size of a pleco can vary depending on the species. Check the following table to see how plecos vary in size based on the species:

From the tables, plecos can be extremely small but also very large. The listed sizes are average figures – that’s how far big the fish can grow at most.

Find Out: What Do Plecos Eat Besides Algae? 3 Healthy Alternatives

How Long Does It Take for a Common Pleco to Grow Full Size?

It takes 5 years for a common pleco to grow to full size. During the first year, growth is exponential, and the pleco reaches about 8 inches (20.32 cm) quickly. After the first year, it begins slowing down.

That said, expect a growth spurt of over half an inch (1.27 cm) per month during the early stages of growth. However, sexual maturity might take longer – up to 10 years.

The growth rate of your pleco will depends on the following factors:

1. Tank Size

The amount of space you provide your pleco determines how fast or slow it grows. This fish needs enough space for free movement.

So providing a large capacity tank is the only way around this aspect. Consider a 150-gallon (567.81-liter) tank—the perfect option to raise your pleco to full size much faster. 

Even though there are tanks with a 30-gallon (113.56-liter) capacity, don’t limit your fish from proper growth unless you decide that’s how you want it to be. 

Some aquarists put juvenile plecos in small tanks while expecting to change them to bigger tanks when they overgrow the small ones. It’s not a great idea because your fish still won’t grow as desired. Let your fish begin life in a larger tank right off the bat. 

The principle is simple, the larger the tank, the faster your pleco fish’s growth; the smaller the tank, the slower the growth.

Also Read: Pleco Fish Swimming Upside Down: 4 Causes and Solutions  

2. Diet

Feeding your fish a good diet should be a priority. 

A well-balanced diet keeps your pleco healthy and promotes smooth growth and development. 

The following are the components of a good and healthy pleco diet:

• Driftwood: Plecos need driftwood because of its high fiber content. Fiber is vital for digestion. 
• Algae-based food: Plecos love algae, so provide algae wafers to supplement the naturally growing algae in the tank. Look for high-quality options that contain a variety of algae species. 
• Fresh vegetables: The diet should have a rich supply of fresh vegetables such as spinach, cucumber, lettuce, peas, and zucchini. Wash and blanch the vegetables before giving them to the fish to increase digestibility. 
• Meat: Apart from the plant-based diet, plecos love meat protein. That’s why you should provide enough earthworms, bloodworms, and shrimp. 
• Fruits: Provide non-acidic fruits like papaya, honeydew melon, breadfruit, and cantaloupe in small quantities. Avoid acidic fruits such as oranges and citrus. 

With this diet, your pleco will be very healthy, and its growth will accelerate. 

Remember to stick to a regular feeding schedule to avoid starving the fish. Feed the fish more often and provide enough food – that’s what will enhance consistent growth. 

As you ensure enough food, be careful not to overfeed your pleco because of overweight issues. 

Moreover, too many leftovers in the aquarium can acidify the water and compromise its quality.  

3. Water Quality

It’s crucial to maintain optimal water quality for your pleco’s proper growth and health. You want to monitor aspects like: 

• Temperature: The correct temperature range for the growth of plecos is between 74-80℉ (23.33-26.67℃). If the room temperature is below 74℉ (23.33℃), use an aquarium heater to maintain the correct levels. Temperature determines oxygen availability, immunity and disease resistance, and the metabolic rates of the fish. 
• pH level: For optimal growth and accelerated development of your pleco, water should be maintained between a pH of 7.0 and 8.0. 
• Ammonia: Despite being a hardy fish species, plecos can be stressed and die when ammonia levels increase. Ammonia should not even be detected in the aquarium. 
• Nitrates: Keep the water nitrate levels between 20-40 ppm. Too much nitrates in water can also limit the proper growth of your fish. 
• Dissolved oxygen: Dissolved oxygen levels should be maintained at a concentration of 5mg/L. This concentration promotes optimal growth and a healthy lifestyle. Low dissolved oxygen concentrations can lead to stunted growth and death of the fish. 

All the aspects mentioned above determines water quality in the aquarium. Therefore, your fish’s growth will be hampered if they’re sub-optimal. 

Another aspect of water quality you should remember is water circulation and infiltration. The more you ensure free water circulation and infiltration in the tank, the better quality and the more oxygenated it becomes. 

Plecos prefer well-oxygenated water. The growth of this fish is greatly hampered if the aquarium is polluted.  

3. Parasites and Diseases

Health issues, as you would guess, can significantly affect your pleco’s growth. 

Parasitic infections like ich affects the fish’s skin. They cause white spots that appear as cysts on the skin. 

Bacterial infections common in plecos include the white fungus disease that causes fluffy cotton-like white or grey threads on the fish’s body, head, and tail. 

Diseases and parasites will slow your pleco’s growth. Even worse, they could kill your wet pet if not managed appropriately. 

How Big Is a 1-Year Pleco?

A one-year pleco should be 6-8 inches (15.24-20.32 cm) big. But the size depends on the pleco species and the environmental conditions provided in the aquarium. Different pleco species have varying growth rates. 

The fish might get big quite fast during the first year. However, it’s very common for the growth to slow down significantly after one year. 

Generally, plecos grow slowly compared to other fish species. Reaching one year doesn’t mean your pleco is now mature. It might take several more years to attain maturity. 

Check out the table below to find out how big different pleco species get after just one year. 

What Size Do Common Plecos Get? 

Common pleco size is 15 inches (38.1 cm) when fully grown under the best care. Nevertheless, the average size can range from 12-24 inches (30.48-60.96 cm) in most aquariums. The 24-inch (60.96-cm) length is only possible in optimal conditions. 

Feed your pleco a balanced diet, as indicated earlier in the guide, to reach the highest growth potential. This fish can take up to 10 years to reach its maximum size. 

Besides proper feeding, you should keep your pleco in a spacious tank, especially if you already know its growth potential and largest size possible. A 150-gallon (567.81-liter) tank is the minimum you can provide for the common pleco to reach its potential. 

Some aquarists start with a 55-gallon (208.20-liter) tank when their plecos are still juveniles. Although this is also an option, it could limit smooth growth. 

The worst decision you can ever make is putting your pleco in a small tank and expecting maximum growth. Small tanks limit the growth potential of a pleco.

Overall, consider a large tank that you won’t have to change in the middle of raising your pleco. Don’t forget the pleco species you have—some are just small in size and would only need a moderately-sized tank.

Final Thoughts

After uncovering some fascinating insights into pleco fish’s growth and size, you can now comfortably answer the question, “How big do plecos get?”

From their humble beginnings as tiny fry, plecos embark on an incredible journey of growth and transformation. 

As we’ve discovered, pleco sizes can vary greatly, depending on the species, age, and tank size, with the potential to reach astonishing dimensions. Therefore, ensure to provide a balanced diet and a larger tank for your pleco’s maximum growth.