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How To Increase pH Level In Fish Tanks – 8 Simple Steps

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By Lindsey Stanton

water checking

Monitoring your tank’s water chemistry is a vital part of keeping a healthy aquarium. Many beginners are often surprised to learn how much science goes on behind those glass walls. That’s why you need to test the water periodically for compounds, such as dissolved oxygen, ammonia, and nitrites. Also high on that list is pH. This term describes the concentration of free hydrogen and hydroxyl ions, which determine the acidity or alkalinity of the water. It uses a 0-14 scale, with 7 being neutral. The lower the number, the more acidic it is. Conversely, the higher the number, the more alkaline or basic it is.

The pH level in your aquarium is one of the most important things that you need to keep an eye on at all times.  For the most part, fish require the pH level to be fairly neutral, or in other words, a pH level of 7. However, some fish need more basic water, up to 7.5, or more acidic water, sometimes as low as 6. Having water that is too basic or too acidic can have truly disastrous consequences on the plant life and the fish in your aquarium.

So, if the water in your tank is too acidic, you need to increase the alkalinity, or pH level. How to increase the pH level in an aquarium is a question we are often asked, so we are going to do our very best to answer it right now.

aquarium plant dividerThe 8 Steps To Increase The pH Level In Your Fish Tank

Saltwater coral reef aquarium at home is most beautiful live decoration
Image Credit: Vojce, Shutterstock

There are a few different methods of raising the pH level in an aquarium. Let’s go over some of the best, fastest, safest, and easiest ways of raising the pH level, or in other words, the things you can do to make it less acidic and slightly more basic.

Step 1. Determine the Ideal pH for Your Fish.

This task is one that you shouldn’t neglect, or else all your subsequent efforts are for naught. Please do your homework and figure out the best pH for your community of fish. If you have more than one species, it’ll likely end up as a range. We recommend following this step before adding any more fish to your tank.

Step 2. Test the Water in the Tank.

Testing the water before you start making changes will give you a baseline from which to begin. It’s also something that you should do after each step. You may find that one small thing makes a big difference. We suggest using the same brand and type of test kit to ensure that you’re getting accurate results.

hand holding PH test
Image Credit: M-Production, Shutterstock

A Word About Test Kits

You don’t need to get a test kit that covers the full scale. In fact, you need something more precise that falls into the range that aquarium fish prefer. That’s why you’ll see test strips with smaller ranges, such as 6.0-9.0 pH, in small increments. These products are more useful because of the meaningful information they provide.

Test strips are notorious for their short shelf-life. It’s one case where less is more. Buy a kit with a dozen or so test strips to help you monitor your progress as you raise the alkalinity in your freshwater aquarium. This way, you won’t waste them.

Step 3. Remove Tank Décor That Acidifies the Water.

Many things can alter the aquarium’s pH. For example, peat moss or driftwood can lower it because of the acidic organic compounds that they contain. Likewise, softened water will have the same effect. You might consider opting for bottled water when you do your next water change. Give it a few days and test the water again.

Step 4. Boost the Dissolved Oxygen in Your Aquarium.

High levels of carbon dioxide can also lower the tank’s pH because of its acidity. A quick fix to that problem is to hook up an air pump and run an airstone to agitate the surface of the water. That will bring down the carbon dioxide levels and increase the dissolved oxygen concentration at the same time. Test again after a couple of days.

aquarium air pump
Image Credit: Pavel Kruglov, Shutterstock

Step 5. Add Items That Can Increase Alkalinity (the pH).

While some things can lower the pH, other items can increase it and raise the alkalinity. Coral or seashells contain limestone, which can get the job done in a non-invasive way. Crushing the pieces will increase the surface area for quicker results. Test the pH again.


One of the things you can do to raise the pH level is to add some crushed coral into the aquarium. You can add it in a cloth bag so that it does not get out into the water, or you can also add it to the substrate.

Crushed coral usually contains quite a bit of calcium carbonate, a substance that will raise the pH level. The effect of this will be gradual and fairly slow, so don’t add too much at once because very quick pH changes can kill your fish outright.

Image Credit: Vojce, Shutterstock

Dolomite Chippings/Shavings

Another substance you can add to the water to raise the pH level is to add some dolomite chippings or shavings into the water. It looks like multi-colored gravel, which is why many people use it for its nice look, but it can also raise the pH level in the water.

Dolomite is very rich in both calcium and magnesium, so it does a good job at raising the pH level. It does work a little quicker than the coral, but this can also be bad due to the quick change that may ensue. The best way to use dolomite chippings is to add them into the filter, at least if you do not want to use them as substrate.

Limestone Chunks

Limestone looks very nice, so that is always good, plus it contains a whole lot of calcium carbonate, so it will raise the pH level in the tank. Be sure that you do not use too much limestone because it has quite a bit of calcium, so the pH changes it causes can be quite drastic.

You might want to remove the fish from the water before you make any changes to make sure that the limestone does not raise the pH level too much while the fish are in the water.

Limestone is fairly cheap, which is another reason why a lot of people use it to raise the pH level. There are also some other rocks with lots of calcium that can raise the pH level, such as travertine, oolite, tuffa, and aragonite.

Macro Algae

Don’t worry, this is not the kind of algae that tends to explode into huge blooms and take over your aquarium. Macro means big, so this kind of algae is not that small stringy stuff.

Macroalgae can absorb carbon dioxide and other chemicals which can cause the pH level of the aquarium water to lower. This is probably the cheapest option you can go with compared to all of the ones we have looked at so far.

Baking Soda

Baking soda is extremely basic, so even small amounts will cause pretty big pH level increases. You do want to remove fish from the water before adding the baking soda, just in case you add too much of it.

1 teaspoon of baking soda for every 5 gallons of water is enough to raise the pH level, but not too drastically. Always be sure to measure the pH level before and after adding any amount of baking soda to the aquarium water.

Step 6. Do a Partial Water Change.

It’s essential to proceed cautiously to avoid stressing your fish and live plants. Siphoning the substrate can remove the debris and waste that is lowering the pH. We recommend starting slowly, with a 10% water change. If you have hard water, that will help too.

A man with hose and bucket, changing the water in a well planted, large aquarium
Image Credit: hedgehog94, Shutterstock

Step 7. Use a Chemical Solution.

It’s imperative to follow the instructions to the letter for the amount of conditioner that you should add for your tank’s size. Another DIY hack is to use 1 tsp of baking soda per 5 gallons of water. Bear in mind that these options may cloud the water temporarily.

Step 8. Maintain the Correct pH.

Now that you’ve raised your aquarium’s pH, you need to maintain it. Carbonate and bicarbonate can stabilize your tank’s water chemistry by acting as buffers to keep it in check. You’ll also find products that can do the same thing. The goal is to keep changes to a minimum to safeguard the health of your fish. Of course, that also includes testing the water regularly.


ph nitrate ammonia fish tank aquarium test
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starfish 3 dividerFactors That Influence pH Levels In Aquariums

Getting the right pH level in the aquarium can be fairly difficult, especially when looking to maintain that level over a long period. The problem is that many different factors can affect the pH level in your aquarium.

Let’s go over the biggest factors which can change the pH level in your aquarium right now.

  • One of the things that can change the pH level in your aquarium is the water you use when performing water changes. The best way to deal with this is to simply measure the pH level of the water you use before putting it in the aquarium. That way you can make adjustments to the pH level of the water before you even put it in the aquarium. Using soft water that has been treated and is low in dissolved minerals is often very acidic.
  • Carbon dioxide is known to lower the pH level of the water. CO2 is great for plant life, but not so much for fish. If you are adding CO2 to the water, you might want to add a little less. This way it will raise the pH level.
  • Generally speaking, increased aeration and higher amounts of dissolved oxygen in the water will increase the acidity of the water. In other words, it will lower the pH level. Therefore, you can try making the water less aerated to raise the pH level and make the water more basic. This can be a little tricky because your fish do need oxygen to survive.
  • Driftwood (we have covered our top 10 list here) and rocks are often very basic, so when you add them to an aquarium, they can lower the pH level quite significantly.
  • High levels of nitrates can cause a drop in the pH levels of the water. Therefore, if you want to increase the pH level in the water, you need to get rid of nitrates. This is best done with a bottle of nitrate-eating bacteria or simply by making sure that your biological filter is working properly.
  • Pollutants, chemicals, toxins, and fish waste, especially ammonia, will cause the pH level in the water to drop. The best way to deal with this issue and raise the pH level is to make sure that you engage in regular water changes to remove these chemicals. Making sure that the filter in your aquarium is working properly will help with this too.
  • Water purifiers are known for lowering the pH level in the water. This is sometimes unavoidable as you might need to use a water purifier for one reason or another.
  • Aquariums that are overstocked can also have a low pH level. This is due to several reasons, but the point here is that if you remove some plants and/or fish from the water, it should raise the pH level of your aquarium water.

aquarium plant dividerConclusion

At any rate, your best bet is to always measure the pH level of the water to make sure that you know where you stand. Once you know, you can take the appropriate steps to raise the pH level and correct the problem. The proper pH level is crucial for ensuring the survival of both the plant and animal species that are in your tank.

Image Credit: Joan Carles Juarez, Shutterstock

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