A stable pH is vital for a healthy aquarium environment.
And before you go adjusting your pH, you should ask yourself: does it need to be adjusted?
Most tank bred fish can adapt to a wide range of pH and if there are no signs of distress, you shouldn’t go messing with your pH.
However, if your pH is low and you have to raise it, use these safe methods to raise pH in your aquarium and keep it stable.
Table of Contents
What Causes Low pH in an Aquarium?
Let’s start by diagnosing the key causes of low pH aquarium water.
Usually, the culprit behind low pH in an aquarium is poor maintenance.
As fish waste and uneaten food collect in the aquarium, they break down and put off more and nitrate (NO3-). Nitrate is acidic. So, the more it builds up in the water, the more it drives the pH down.
The best way to maintain a healthy pH in your tank is usually by just doing routine maintenance on your tank each week.
For more information about nitrate in the aquarium, check out our Aquarium Nitrogen Cycle article.
Check Your Tap Water
I highly recommend that you check the pH of your tap water. If your water has a good pH out of the tap, then all you need to do to bring up the pH in your tank is perform water changes.
You can perform 50% water changes every other day until the water in the tank is in a good range. Then, you can usually get away with just doing one 50% water change each week to maintain healthy water parameters.
Another thing that can drop your pH is decor that leaches tannins. Tannins are organic compounds produced by plants that help protect them from fire, insects and microorganisms.
Tannins are acidic and can bring down pH in your aquarium.
The most common source of tannins in the aquarium is driftwood. The wood releases the tannins into the water, staining the water brown and dropping the pH.
So, if your water has a slight brown tinge to it, and your pH is dropping, then something in the tank is putting off tannins.
I highly recommend boiling driftwood to help release tannins before you put it in the aquarium. If the wood has a lot of tannins, you’ll see the water turn brown, like when you boil tea leaves.
If the water turns a really dark brown, dump it and boil again with fresh water. Keep doing this until the water stays clear.
If the driftwood is too big to boil, soak it in salty water (½ cup of salt per gallon of water) for 1-5 days. This should clear off a lot of the tannins and hopefully keep them from affecting tank parameters.
Other organic sources of tannins include leaves (especially Indian Almond Leaves) and alder cones.
If CO2 from fish respiration builds up in the water column, this can also drop the pH. This is one of the reasons that it is highly recommended that you use a filter in your aquarium.
A lack of aeration is one of the reasons that the pH is horribly low in unfiltered Betta tanks.
Filters help move water around the aquarium and agitate the surface, allowing for better gas exchange.
You can also increase aeration by using an aquarium air pump with an airstone. The bubbles increase water flow and surface agitation.
Is Low pH Bad for Fish?
Yes, severely low pH is bad for fish. But, what exactly constitutes “low pH?”
When I say low pH, what I mean is below 6.5. There are some species that thrive in water that is really acidic, but the vast majority of fish you find in the aquarium trade don’t like the pH that low.
Also, when the pH is below 6.5, the water usually doesn’t have the buffering capacity to prevent the pH from crashing even lower.
But, if your pH is 7.0, but you read an article that says the species of fish you’re keeping likes a pH of 7.5, trust me, there is no need to try and add chemicals or filter media to raise your pH.
Most fish can tolerate a wide range of parameters, as long as you carefully acclimate them, perform regular water changes and keep your water parameters steady.
I can’t possibly emphasize this enough: you will have much more success by keeping the conditions in your aquarium stable rather than trying to constantly mess with your water parameters trying to achieve the “perfect” numbers you read about in an article somewhere.
When you see bloggers (myself included) post “ideal” water parameters, things like pH, KH and GH, those numbers are based on the conditions from the fish’s natural habitat.
But, the overwhelming majority of fish you see in the hobby have been tank raised for many, many generations and therefore can adapt to most conditions found in home aquariums.
More often than not, fish can adapt to a wide range of parameters.
The things that are really important are providing a well cycled aquarium, a steady temp and routine maintenance that keeps your nitrates below 30 ppm.
So, for the record, you likely don’t need to increase the pH in your tank.
How To Raise Your Aquariums pH
OK if you’re still determined to do it, here’s how to do so safely. In general, I do not recommend the chemicals you see on store shelves. They can cause massive swings in your pH and then wear off after a few days.
If high nitrate in your tank is dropping the pH, the best treatment is to change out aquarium water. You can perform 50% water changes every other day until the pH comes back up.
Once you’ve got the pH under control, you can maintain healthy parameters by performing 50% water changes every week to remove nitrates and add in clean water.
Baking soda (sodium bicarbonate NaHCO₃) increases the KH and pH of water.
You can add 1 teaspoon of baking soda per 5 gallons (19 liters) of water. Just remember, most aquariums have a bunch of other stuff in them that takes up space and decreases the amount of water in the tank.
For example, if you have a 10 gallon tank with substrate and decor, it is holding less than 10 gallons of water.
I recommend that you err on the side of caution and go slowly.
Add doses, then wait a day or two, and then add more, until your desired pH is reached.
To maintain that pH level, you’ll need to add more baking soda every time you perform a water change.
Be extremely careful when making changes to the pH of your aquarium with any kind of chemical. Making large changes to your pH in a short period of time can shock and kill your fish. I recommend that you make small adjustments over time.
Crushed Coral/Aragonite Sand
Crushed coral and aragonite sand are both made from the same material: calcium carbonate. The only real difference is that crushed coral is in bigger pieces, like really jagged gravel, and aragonite sand is made up of much smaller particles.
You can add crushed coral in a bag to your filter or use aragonite sand as your substrate. Both will leach calcium and carbonate into the water column, increasing both the GH and KH. As the KH increases, so will the pH.
Aragonite sand is my number one recommendation for substrate to use with African cichlids. Over time, the leached minerals will naturally raise the pH in a stable and safe way. Plus, the cichlids will love digging around in the sand.
Also, there’s no need for you to add something every time you do a water change, the sand will do it for you.
Don’t Chase pH!
Again, I would really like to emphasize that keeping your pH stable is much more important than trying to achieve the “perfect” pH.
Most often, all that’s needed to maintain a healthy pH is routine water changes to remove wastes and add back in clean water.
Ping-ponging the pH all over the place with chemicals does way more harm than good.
I can’t even count how many horror stories I’ve seen over the years on forums of someone saying, “I added pH up, but then it went all crazy high, and so I had to add pH down, but then it went way too low, so I added more pH up, and now all the fish are dead.”
Steady and stable is so much better and safer than constant tinkering trying to chase imaginary “perfect” numbers.
If you do need to bump the pH up a bit, I highly recommend adding crushed coral or aragonite sand. These will naturally buffer the water to a higher pH over time.