What You Need to Know About The Ideal Pleco pH Level

Betta ebook-ban

Last Updated on 2023-05-24

The suckermouth catfish, also known as pleco, is a popular choice for many people. They’re nice to have in the fish tank for their elegant looks and peaceful nature. But to keep your pleco healthy, you need to achieve a proper pH balance of water in the fish tank. What is the ideal pleco pH level? You’ll find out below. 

What Is the Ideal pleco pH level? 

Generally speaking, Locariid catfish in the wild are found in soft water where the pH level is low. That being said, many species sold commercially today are raised to tolerate higher pH levels.

For most captive-bred plecos, pH between 7.0 and 8.0. On the other hand, wild-caught plecos may require pH between 5.5 and 8.4.

What Happens if the pH Level Is Too High? 

To create optimal conditions for the pleco fish in the aquarium, the pH balance is crucial. Before getting the fish, it’s useful to learn more about pH balance in order to avoid high or low values. Below you can see what happens if the pH level in the fish tank is too high. 

Your Plecos Will Be Affected 

High alkalinity, i.e., excessive pH levels, can negatively affect the development and health of the fish in your aquarium. For instance, too high pH level can dissolve the protective mucus layer on the skin of pleco fish. When this protective layer is damaged, the fish become vulnerable to bacteria and infections, which can harm their health and cause complications that shorten their lifespan.

Nontoxic ammonia becomes toxic due to high pH, which may lead to breathing difficulties. Additionally, excessively high pH levels in a fish tank can harm the pleco’s fins and tails, damage their growth, and even make them look ragged. The highly alkaline environment doesn’t allow the fish to thrive, and they eventually die.  

Disrupted Uptake Of Calcium 

Some people tend to increase the pH level in their fish tanks to accelerate the growth of corals. However, pH balance is not something we should mess with, especially when it comes to fish health and wellbeing.

When discussing the negative impact of high alkalinity, it’s useful to mention it can disrupt the uptake of calcium by fish in the aquarium. Fish and other organisms need calcium for growth and development. Excessive pH levels don’t allow that to happen.  

Aquarium Issues 

Excessive pH levels not only harm the fish but also cause problems with the aquarium and equipment. Since high alkalinity disrupts the uptake of calcium by fish, the excess of this mineral precipitates out of water.

This leads to various problems as this mineral can form coatings on filters, the pump, and the heater. It can also blur out your view into the fish tank. Problems with equipment don’t allow proper oxidation and filtering of water, which can also manifest itself through health problems affecting your pleco fish. 

File:Hypancistrus Zebra Pleco Juvenile.jpg - Wikimedia Commons

What Happens If the pH Level Is Too Low

Highly acidic or low pH occurs due to excess carbon dioxide, tannins from driftwood, the nitrification stage of biological filtration, and other causes such as lack of experience to maintain proper pH balance. Below you can take a look at the effects that may happen if the pH level is too low. 

Excess Mucus 

Increased acidity in the fish tank may induce excessive production of mucus by the pleco and other fish in the aquarium. This happens due to the elevated presence of toxic elements promoted by the acidic environment. Excess mucus increases stress on fish in the aquarium and makes them vulnerable to potentially lethal secondary infections. 

Fish Gasping  

The high levels of carbon dioxide in the excessively acidic aquarium may cause problems such as fish gasping. In other words, your pleco can’t breathe properly and is in distress. When stressed, fish don’t eat properly, and lack of oxygen can put them in grave danger. 


Chronic exposure to highly acidic water in the fish tank can lead to hyperplasia i.e., enlargement and thickening of gills and skin. This severely affects the structure and function of the gills and predisposes them to further bacterial colonization. 

Eye Damage 

Yet another major consequence of a highly acidic environment is the potential eye damage your pleco fish can experience. Besides eye damage, too low pH can also lead to severe complications and death. 

(Find out whether the 15 most common plecos are right for your tank!)

betta care facebook group

How to Lower the pH Level In the Tank? 

As seen above, a highly alkaline fish tank can harm the fish, but also damage the equipment. Fortunately, there is a lot you can do to lower the pH level in the aquarium and thereby create an optimal water environment for your fish. Below you can take a look at easy strategies. 

Perform Partial Water Changes Regularly

The biggest reason why the fish tank is too alkaline is almost always the elevated levels of ammonia. That’s why one of the easiest things to do in order to lower pH is to perform a regular water change. This will allow you to eliminate fish waste and leftover food in the tank, thereby decreasing the presence of ammonia and lowering pH. 

Change The Filter 

If the filter in a fish tank is old, it may not be able to do a good job anymore, which could be the reason why the pH level in the water has increased. Consider changing the filter or ask someone to take a look at it to ensure it’s working properly. 

Add Peat Moss Into The Aquarium

An easy way to lower pH in the fish tank naturally is to add peat moss, which you can do in different ways. Available in the form of pellets and chinks, peat moss can be added directly into the filter or placed anywhere in the fish tank. When it comes to peat moss, you need to bear in mind that adding it directly to the fish tank can be harmful as it releases a yellow tinge, so it’s useful to submerge it into a container for a few days before transferring it to the aquarium. 

Add Driftwood To The Fish Tank

Driftwood is usually found in the natural environment, so adding it to a fish tank could create the ideal conditions for your fish. You don’t need to add too much; a piece or two is enough to filter the water and help lower pH levels by releasing tannins. 

Lower Aeration In The Aquarium

Decreasing oxygen in the fish tank will slightly elevate carbon dioxide levels and thereby reduce pH. This method is easy and cost-effective, but you do need to be careful. Always keep in mind your fish need oxygen to survive, and if you overdo it, the consequences could be severe. 

Reverse Osmosis

The process of reverse osmosis (RO) removes many ions and molecules from water, thus making it cleaner. A partial semi-permeable filter and RO can remove nearly all contaminants successfully. Unlike other options on this list, reverse osmosis is more expensive, but at the same time, it’s the most effective way to lower pH in the fish tank due to the high precision that other methods can’t meet. 

Ancistrus - Wikipedia

How to Raise The pH Level In The Tank? 

Just as high pH is harmful to the pleco in your fish tank, highly acidic water is dangerous too. The good thing is that you can raise the pH level in the aquarium and improve the health of the fish in it. Below, you can find some useful suggestions. 

Crushed Corals

Probably the easiest and most effective way to increase the pH level in the fish tank is to add crushed corals and shells because they are abundant in calcium carbonate compounds. Their greatest advantage is the improvement of pH balance without harming fish. 

Dolomite Chips 

Dolomite chips are more than pretty decorations in the fish tank; they are important for increasing pH value in the aquarium. Just like crushed corals, dolomite chips can increase pH levels without putting fish in danger. They do so by delivering calcium and magnesium, both of which are important for pH balance. 

Try Adding Baking Soda

Adding baking soda can raise the pH levels of the aquarium water, but you need to be careful and avoid overdoing it. Also, you may need to do it more often. This is not a scenario where you add a little bit of baking soda, and you’re set from that point on.  


In this post, you’ve had the opportunity to learn what is the ideal pleco pH level and how to increase or decrease it. If you’ve never had a pleco or any other fish in the aquarium before, you need to make sure the pH level always meets the needs of that particular species.  

(If you’re keeping angelfish, guppies, mollies, gouramis, cory catfish, or cardinal tetras, then you may be interested in their ideal pH levels as well!)

Ultimate Betta Fish Care Guide
About the author

Hey! I'm Nicolas from Iguane Media !

Blogger and Owner of the betta care fish guide
Thanks for reading this blog

I'm an Animal Lover