How to Maintain Ideal Molly pH Level in the Aquarium – Complete Guide

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Last Updated on 2023-07-31

Taking care of exotic fish takes plenty of dedication and focus; mollies are no exception. Maintaining proper water quality for mollies should be your top priority. That’s where providing the ideal molly pH Level in the fish tank comes into play.  

Since these species belong to a delicate ecosystem, they need cautious and constant care. To thrive, you have to supply them with a substantial environment. This is a detailed guide on how to maintain proper pH levels in the tank when taking care of mollies.  

What Is The Ideal pH Level for Mollies? 

Mollies require a stable living space and hard water from 15 to 30 dGH. Every type of molly prefers a unique water pH. But, in general, the perfect molly pH Level can range from 7.5 – 8.5 and provide the fish with an adequate environment to live in.  

Why Do You Need to Maintain Ideal Molly pH Level in the tank? 

Fish are very vulnerable creatures. With even the slightest changes to their environment, they are exposed to stress and disease.  

Simply put, when you don’t provide the optimum molly pH level, the water will start to affect their basic bodily functions and interfere with their life. These changes will leave a massive impact on new fish, and they are less likely to breed.  

How Do I Examine the pH Levels? 

To provide the tank with an excellent molly pH level, you have to often monitor your aquarium. Luckily, this is a very easy task to do.  

All you’ll need is a proper pH testing kit you can get at any pet store or Amazon. These kits come in various shapes and sizes, but the most used ones are the simple strips. They are designed to point out any changes in the water. Simply dip the strips in the water and wait for the color to indicate the level.  

How Often Should I Examine the pH Levels? 

Examine the tank at a minimum of 2 times a month (once every two weeks). That way, you can monitor for any changes in the water and detect the problem in its early phase. But, do have in mind that the pH levels can differ based on the time of the day. So, test the water in the afternoon for the most reliable results.   

Note: If you are adding new objects to the aquarium, like new decorations, plants, or fish, you should test the molly pH level after you introduce them to the tank.  

orange molly | nice colors on this one | h080 | Flickr

What Happens if The pH Level Is Too High? 

Too high pH levels create a highly alkaline environment. Due to the high alkalinity, the mollies can suffer serious health problems.  

Some mollies can tolerate high pH levels, and others won’t. The longer they remain in a high alkaline environment, the more their mucus layer (the body’s protective layer) starts to dissolve, exposing them to bacteria and infection. In the end, the fish become very vulnerable to disease, which will highly reduce their chances of survival. That’s why maintaining a proper molly pH level is essential.  

What’s Making the pH Levels Rise? 

When we expose tap water to the air, it starts to agitate the surface of the tank, resulting in gas exchange. The airborne oxygen will enter the aquarium, while the carbon dioxide will leave the aquarium and go into the air.  

The less carbon dioxide remains in the aquarium, the higher the pH levels are going to get, assuming there aren’t any pollutants affecting the pH levels in the tank.  

What Happens If The pH Level Is Too Low? 

Low pH levels can make the mollies very sick and increase their chances of premature death. The water is incredibly acidic and toxic for their health, particularly the younger fish.  

Old fish can stay alive in this unhealthy environment since their bodies are already accustomed to the chemical balance in the water. But, as the bacteria level starts to build, the rest of the fish will soon notice the imbalance. 

What’s Making the pH Levels Drop? 

When the pH levels drop, it is usually due to the “old tank syndrome.” Because of poor water maintenance, the ammonia levels get too high and drastically reduce the pH levels.  

This can also happen when we add too much new water to the tank without carefully taking care of it. Maintaining an adequate molly pH level prevents that from happening.    

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How To Lower The pH Level In The Tank? 

If you notice that the fish look ill or lack energy, it means they might not have the oxygen they need. Keeping the ideal molly pH level will be critical. There are many ways you can lessen the pH level if it’s too high. Here are a couple of options that can make that happen.  

Add Driftwood To The Tank 

This natural item releases tannic acid and slowly reduces the pH levels in the tank. It is a completely natural process that doesn’t expose the fish to harmful chemicals or preservatives. This element is the perfect short-term option for dropping the pH levels.  

Remember to soak it before you put it in the aquarium. 

Prepare Peat Moss 

Peat moss and driftwood have similar properties. As long as you get real peat moss, it can drop the pH levels in the water and keep them stable. Only use the moss meant for fish tanks so you won’t expose your fish to chemicals.  

Decorate the Base of the Tank With a Few Almond Leaves  

This is another natural option for decreasing the pH levels. These leaves release tannic acid and provide the perfect hiding spot for your mollies. However, do have in mind that the leaves can make the water turn yellow. This is a normal chemical reaction.  

File:LyretailMolly.jpg - Wikipedia

How To Raise The pH Level In The Tank? 

When it comes to pH level raising techniques, it’s vital to pay attention to the state of the water before adding any chemical treatments.  

For the mollies to strive, the typical molly pH level should be relatively high. If it drops too low, it’s best to try a few natural methods to bring it up again. Here are a few pH level-boosting techniques you may want to try.  

Add Texas Holey Rock, Limestones, Seashells, or Crushed Corals 

All of these components contain natural minerals that can boost the pH levels in the tank. If you pour some of them into the aquarium, you will be able to increase the pH.  

But, do have in mind that you can’t go overboard. With every component you add, you need to test the pH level to control the quantity of the items you add. 


Macroalgae create an actual seabed, perfect for mimicking the molly’s habitat. Unlike other useless algae, this one has the capability to raise the pH levels and provide a healthy living space. The plants are not difficult to manage since they will grow on their own. Just make sure they don’t grow too much and take over huge sections of the tank.   

Change the Water in the Tank 

Over time, pollutants will start to build up, either from the decaying food or the fish waste. The longer these pollutants remain in the water, the quicker the pH levels will drop.  

So, do routine cleaning and replace the water. Add the water a bit by bit to avoid shocking the fish. But also, be gentle, since mollies are very soft species.  

Use Dolomite Chips 

Dolomite chips are gravels with different shapes and colors often used in aquariums. They are not just there to make the tank pretty; they are used to boost the pH level. But, most importantly, they don’t have any negative effect on the fish.  

Instead, they are packed with magnesium and calcium, which are essential for a healthy living environment. 

Take Out the Driftwood 

If you’ve used too much driftwood as a décor, it could be dropping the pH levels a lot faster than you might expect. This item is responsible for releasing tannins and softening the water. So, you might want to get rid of it for the time being.  


Water stability will be your fundamental component in keeping the mollies happy. You will need to provide them with a healthy and clean environment. The only way to make that happen is by maintaining proper water quality in the fish tank.  

Of course, it’s impossible to tell the pH level just by looking at the tank, but with regular water testing, you will always be on the right track. It’s important to invest in filters and adequate maintenance to ensure an optimum living space for your mollies.  

Change the water often and maintain relatively high pH levels. Your mollies will thrive in this perfect environment.  

If you have other fish such as cardinal tetras, plecos, gouramis, cory catfish, guppies, or angelfish, then you should check out how to maintain their ideal pH levels as well!

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