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Natural Ways of Lowering pH in Aquarium

A sudden behavioral change in your finned friends, such as gasping on the surface or odd swimming patterns, calls for a quick check on the water condition because most of the time, this is where their stress comes from.

Has the water become more alkaline because the pH scale is above neutral upon testing? If so, you need to lower the aquarium ph. But before you do that, let’s reconfirm first if your aquarium needs careful and safe pH adjustment.

Aquarium 101: The power of Hydrogen (pH)

PH refers to the acidity level of water. Its measurement is on a scale of 1 to 14, with 7 being the neutral value. Values lower than 7 are considered acidic, while higher values indicate more alkaline in the water. Even though there is no such thing as a normal pH level, you have to know the species of fish that you have so you can build the right environment for them.

Most fish are adaptable to their environment, especially those that are tank-bred as they are more tolerant of varying water chemistry. Thus, a slight increase or decrease in the level of acidity and alkalinity of the water should not be a problem unless you see your finned friends nowhere near calm. In that case, get your testing kit right away.

Suppose that you have the saltwater species, the preferred pH level is between 8 or higher. Freshwater species should have at least a pH level of 5.5 to 7.5. Any drastic rise in the pH level is lethal to your aquarium buddies.

What Triggers the Rise in pH Level

Calcium-rich materials

Making your aquarium beautiful is normal, but you should do it with caution and proper research. Sometimes, the rise in pH is caused by rocks and other fixtures that you put as decorations. Limestone is just one of the usual rocks that can elevate pH level because it leaches calcareous, which contains calcium.


Aeration is a process of increasing the oxygen concentration in the water that drives down carbon dioxide by letting it escape from the tank, which translates to higher pH. You can still use aeration if you need to adjust your pH level in case it went too low, but you may want to use an air stone to aid you in slightly increasing alkalinity.

Algae and Slime Growth

Placing a lot of aquatic plants in your aquarium may trap carbon dioxide and other harmful materials like nitrates, which may result in algae and slime clinging to the plants, decorations and even on the glass. These materials do not only ruin the pH stability but also harm the fish.

Aside from aquatic plants, algae are mostly caused by overfeeding, a high fish stock with few plants, or inappropriate partial water change. In case of heavy algae infestation, you can introduce algae-eating snails and grow healthy aquatic plants that feed on algae.

Irregular Cleaning of Filter

It may sound so simple compared to other causes, but not cleaning your aquarium filters can dramatically disturb the water condition. Take note that cleaning should be done still with caution and proper knowledge because whether you like it or not, both good and bad bacteria live there. You don’t want the good ones to leave too.

You should clean your hang-on, sponge, canister, under gravel, and in-tank filters partially and not so frequently. Also, you should be able to identify accumulated rotting or decayed organic materials and debris and get them out.

How to Naturally Lower pH in Aquarium

Various chemical solutions are available in the market to help to lower the aquarium pH such as those labeled with “pH reducer” and “water softener.” Commercial distilled white vinegar can also be used but with the right measurement because its acid can bring down the pH harshly. Always remember that too much of something is always poison.

To be on the safer side, you can do the job by using the following:

1. Peat Moss

These are dark brown, dead fibrous products after mosses and other decayed plant matters decompose in peat bogs without artificial additives. It can reduce pH by filtering out contaminants. According to Robert Boumis of The Nest, you can simply incorporate peat moss in your aquarium by following these steps:

  • Put the peat moss inside a pair of clean nylon stockings and tie it off.
  • Boil it in a separate bowl until the water turns black.
  • Pour the liquid that leaches out, squeeze it out, and then rinse.
  • Add the untied stocking to the hang-on filter, sump, or empty compartment in the canister filter so it can do its job absorbing various minerals and releasing tannins.

To ensure that you don’t overdo the peat moss procedure, you should start with small amounts and monitor it and your fish. If no adverse reaction, you can steadily adjust the amount.

2. Driftwood

Using driftwood is also considered an excellent, natural method of lowering the aquarium pH and works almost the same way as the moss. What makes driftwood more advantageous is that it serves as a natural habitat for fish.

Mike Tuccinardi of the Tropical Fish Magazine, driftwood for aquarium purposes should at least possess the following characteristics:

  • Non-toxic. The driftwood that you choose should not contain any chemical solutions or preservatives because it can leach these compounds into the water and wreak further havoc on your already-compromised aquarium. Tannin is the only acceptable substance that driftwood should leach.
  • If you think that woods easily sink, you’re wrong. Well, as far as driftwood is concerned. This type of wood is buoyant and requires either complete submersion underwater until totally saturated or add some weights to it to make it heavier. Boiling the driftwood to make it sink is another option, but you got to have a larger pot to accommodate its size.
  • Driftwood is already a dead, organic matter. Once you place it underwater, decomposition will soon follow. This characteristic is healthy for your aquarium life because it creates food for your finned friends. However, you may opt for the driftwood with a slow decomposition rate so you won’t be losing an aquarium centerpiece the soonest.

3. Cattappa Leaves

Also known as Indian almond leaves, Cattappa leaves are naturally acidic. It is extremely ideal for your aquarium, especially when you intend to lower its pH level because of the tannic acid it releases. It is a beautiful decoration, but similar to peat moss and driftwood, Cattappa leaves will discolor your aquarium dark brown over time because of the said acid.

Cattappa leaves are not only known for lowering the pH level of the water, but also for being a natural source of antifungal and antibacterial properties in your aquarium that can heal fin rot and support vulnerable fry.

Suppose you are keen on aesthetics and don’t want to see your aquarium brown-tainted, you may put some activated carbon to your filter to make the water clearer. It will lessen the tannins though, which is primarily in charge of pH lowering. If you are prioritizing a healthy aquarium life over aesthetics, then Cattappa leaves is a good choice.

4. Reverse Osmosis

Uncomplicated as it sounds, reverse osmosis (RO) is one simple solution if your water doesn’t have the correct parameters for your aquarium inhabitants. RO is done by using water purifying units that are common in the household. The process simply involves driving out the water molecules via a selectively permeable membrane to bring in water into the aquarium without the hardness and pollution usually found in tap water.

RO efficiently removes up to 99% of water impurities not limited to heavy metals and pesticides. Specifically, RO is very ideal if you have a freshwater aquarium because it enables the adjustment of pH to match the required water parameters of your fish.

5. Regular Water Change

As others would say, “when all else fails,” you should change the water in your aquarium. It is like a reset button when no matter how you try you cannot get the pH level down. However, you must always do a regular check on your aquarium pH before doing this so you will save a lot of time and of course, your aquarium inhabitants.

According to Shirlie Sharpe of The Spruce Pets, the frequency of water change depends on the number of inhabitants and size of the aquarium. You can take note of the following factors:

  • Lightly stocked – Change 10-15% water, not less than biweekly
  • Heavily stocked – Change the water by 20% at least weekly.
  • Average-sized aquarium – Change 10-15% of water weekly.

In every water change, you should always clean the filter and vacuum the gravel during siphoning procedure.


The level of acidity in the water is just one of the several things that you have to maintain at bay to have a healthy environment for your finned friends. You do not have to frequently change the pH as it equates to disturbing its stability. However, if you see red flags then start to perform pH testing and lower the pH level slowly first, then increase the phase if you have to.

There are different ways to lower the pH in your aquarium, which sometimes involve the use of chemical solutions. However, if you can allot a lot of time for needed preparation and procedure, always go for the natural method. It ensures that your aquarium is a lot safer from harmful substances that you do not know exist after using chemicals.



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