Molly Fish pH Level – How to Maintain Ideal Molly pH Level ?
Maintaining a suitable environment for your molly fish can be tricky, especially in terms of ph. Is the water too acidic or too alkaline for them? This article will help you identify the right pH conditions for your pet molly fish. Moreover, I will be highlighting how low or high pH can affect your molly fish, and how to correct this imbalance in ph.
Molly fish live in freshwater which is slightly alkaline in nature. The optimal pH range for molly fish is from 6.5 to 8.5. This shows that these fish thrive well in either neutral or slightly alkaline conditions. This holds good not only for mollies but for many other species of fish as well.
By the end of this article, I will have your doubts cleared about pH maintenance in your molly fish tank, and how some simple tricks in maintaining pH can contribute to the healthy life of your molly fish.
What pH do Mollies like?
In their natural habitat, molly fish are normally found in freshwater and in relatively brackish water, but people have been experimenting with keeping these pets in a marine environment as well. This has worked for molly fish as well. Brackish water has a slightly higher pH than neutral, up to about 8, which is well within the optimal range required for molly fish. Deviation from the normal range of pH can be harmful to your mollies.

pH is Too High (above 8.5)
- High pH means that the water is more on the alkaline side. The high alkalinity of the water causes the protective layer on the skin of the molly fish to break down. Our skin protects us from the harmful environment and diseases around us, and the same goes for your molly fish.
- Their inner skin is prone to catching infections from the water as the outer skin no more exists. This causes diseases and infections and may result in your molly fish dying.
- Lower oxygen levels due to high pH, can make molly fish tardy and cause them to be less mobile and tired.
pH is Too Low (below 6.5)
- Baby molly fish are very sensitive to pH and pH changes. If they are introduced to an acidic environment, their growth is stunted. They may end up dying prematurely.
- Lesser than optimum ph has a relatively lesser impact on the more mature fish, due to resistance being built over time, but be warned that harsh pH conditions can still cause them to die.
- An acidic environment calls for bacteria to be formed, and wherever there is a bacterium, there are parasites and diseases.
Sudden Change in pH
If there is a sudden change in the pH levels of the water in the tank of your molly fish, they might suffer from stress. Stressing the out can easily make them sick as they are very delicate fish in an abruptly changing environment.
Related Post: Why Does Molly Fish Stay at The Bottom of The Tank?
Why Does the pH in the Aquarium Change?
I have always wondered how the pH of an aquarium can change when there has been no addition of chemicals in the water. Why is it that every time I check the pH level of my aquarium, the pH is not what I last checked it to be?
Well, there are numerous factors contributing to that.
pH Increase Automatically
- Use of Tap Water
Most of us use tap water to fill our fish tanks. It is a huge mistake when you are keeping delicate fish such as mollies. Tap water contains added minerals in it and with time, those can react with the surrounding air to produce substances that make the water alkaline (the pH increases).

- Increase in CO2
Molly fish, like any other organism, breathe in oxygen and breathe out carbon dioxide, and for this reason, plants are added to the fish tank that produces oxygen for your molly fish to breathe in. Plants take in Carbon-dioxide from the water, but too less carbon dioxide can make the water in the aquarium alkaline, thus raising the pH level.

pH Decreases Automatically
- Poor Maintenance
If the water in your molly fish tank is not changed regularly, it may cause the water to become acidic and harm your fish.
- High Ammonia Levels
The ammonia gas is acidic in nature. If there is an ammonia gas building up in your aquarium, the pH level of the water in the fish tank will decrease and will result in your molly fish getting affected.

- Water added
Make sure that when you add or change the water in your molly fish tank, you are doing so carefully. Adding water in bulk, without properly measuring the pH of the water, can cause drastic pH changes in the fish tank.

- Pollutants
With time, there are pollutants that build up in the fish tank. These can range from dead plants to fish feces, to dead fish. The accumulating pollutants can also cause the water in the fish tank to become acidic (lower the pH).
pH for Mollies. How to Maintain?
Let me share my personal experience with you. The reason why my molly fish have survived this long is that I regularly maintain their habitat. The habitat that is most suitable for them to live a healthy life.
I will now share some tips that I have found to be helpful in maintaining the pH of the water tank to an optimal range for my molly fish.
Regularly Measuring the pH
- It is ideal to keep the pH level under check over periods of time. I suggest that you measure the pH every 2 weeks, especially when there is a water change in the tank.
- Do note that pH levels can differ during various times of the day, so it is better to check at different times when measuring it, to reach a more reliable conclusion.
- The pH level of water can also vary with the depth of water. So, make sure that when you measure the pH, take samples of water from different sections of depths of the tank for a more reliable measurement.
- Molly fish need plantation and decoration to keep them happy and closer to their natural environment. So, whenever you bring something new into the water tank for your molly fish, do check the pH, as the newly added item might have affected the pH in some way.
Related Post: How Long Does Molly Fry Take to Grow & Reach Full Size?
How to Measure pH?
- pH Paper Strips: These can be used by simply dipping the strip into the water. The color of the strip then indicates the pH value. This is very cheap and easily accessible.
- pH Meter: For more reliable results, and precision, I personally use a pH meter that I purchased from Amazon. It is easy to operate and gives the value of pH closer to accuracy. My personal recommendation is to buy one of the ph meters.

Lowering pH Level
- Driftwood: This is the most easily available and widely used option, as it is completely natural and has zero side effects for your molly fish.
- Vinegar: Use 2 to 3 drops of distilled vinegar in each gallon of your molly fish tank. Do make sure that the vinegar being used is not flavored.
- Sphagnum: More commonly known as peat moss can also lower the pH level without harming the fish.
- Almond Leaves: These are readily available and can be used in dried form as well. All you need to do is to line the bottom of your fish tank with dried almond leaves. A disadvantage to this is the coloration of water to yellow, but it is completely harmless to the mollies.
Raising pH Level
- Removing driftwood: If you have added the driftwood earlier in order to lower the pH, then just remove it from the tank to raise the pH back to optimum for the molly fish. This is a simple and highly effective option.
- Marble, limestone, and dolomite chips: As it is a well-known fact, marble or limestone is alkaline in nature and their addition to water can raise the pH of the water to alkaline. They also add to the mineral content of the water which is healthy for the growth of molly fish. Make sure that while you add these minerals, you keep a check on the changing pH.
- Seaweed: This can not only make your tank appear greener, but also raise the pH level of your molly fish. This is a cheap option in terms of money and time, as it can grow on its own, and provide a natural habitat like that of freshwater for molly fish.
- Marine salt: The addition of salt to make the water slightly alkaline for the molly fish is widely practiced. However, adding salt has no other particular advantage for the mollies, as compared to the rest of the available options.
The Bottom Line on pH For Mollies
As far as molly fish are concerned, their optimum pH levels are relatively easy to maintain. Just make sure to keep a check on the pH levels in their water tank, twice a month at least. This will give you an idea of how to adjust the tank conditions to bring the pH level to an optimum level for your molly fish. If the pH level of your molly fish tank deviated far too much from the optimal range of 6.5 to 8.5, make sure that you follow the guidelines mentioned above to bring it back to optimum. Failure to do so may result in the loss of your beloved mollies, and good pH conditions will keep them healthy, happy, and alive!