How to Lower the pH in Your Freshwater Aquarium

By Eddie Waithaka @aquariawise

How to Lower the pH in Your Freshwater Aquarium and Keep it Stable

Testing the ph in your freshwater fish tank is imperative to help determine if your aquarium is safe for the fish you’re keeping. This is because your fish may succumb to ph shock when introduced to a tank with high alkalinity.

Ergo, try to keep your freshwater aquariums between 6.5 and 7.5, though this may vary depending on your fish tank inhabitants.

That said, the range will not always stay within acceptable limits. There are times when test results are quite basic, meaning the water has a ph spike.

So, today we’ll learn how to lower the ph in a freshwater fish tank.

But first let’s dig a little more into the proper ph for a fish tank and why the water increases in alkalinity. This should lead us to a more informed solution.

The Proper pH of Freshwater Aquarium

Realistically, there is no one proper ph for a freshwater fish tank, and although you may not like this answer, it does depend on the freshwater fish you plan on keeping.

Some fish get by with a low of 5.5, while others are more comfortable with a little more alkalinity; up to 8.5.

For instance, Oscars fish prefer acidic water with a ph of 7.0 on the upside. African cichlids like water that is more basic up to 8.5 and species like goldfish are hardy, hence can live in a wide ph range.

If you have many species like in a community tank, the goal should be to have your aquarium at a neutral of 7.

Also, keep in mind the ph in most fish tanks is not static and will change severally over 24 hours. Typically, in freshwater aquariums, it will drop at night and rise during the day.

So. I recommend you aim at keeping your water ph stable and adjust accordingly in case of a spike.

Sometimes, you may need to raise the ph, but because most water sources are already slightly to moderately alkaline, you will rarely need to.

What Causes The pH to Raise in a Freshwater Aquariums?

There are several factors that raise the ph in your fish tank. Mostly it’s a result of trace minerals in tap water. In turn, alkalinity in natural water comes from the source.

Tap water with high traces of silicate and phosphates and frequently carbonates when added to your tank will consequently raise the ph to above 7.

The other major cause is your substrate. So stay clear of sand substrates because they particularly have quite a high concentration of silica.

There are also some commercial substrate brands in the market, which have chemicals that may have a basic effect on the water.

That said, other causes you should consider are failing filtration systems and certain fish medications.

If a filter fails, there is usually an accumulation of ammonia which can seriously spike your water ph. Also, an inefficient filter, even one that has not failed will still have substantial effects, so will a filter with no proper mechanism to expel excess nitrates.

To stay ahead of this causes, consider using RO water if your municipal water supply has high mineral traces. Plus check the alkalinity of your substrate before purchase and finally maintain your filter accordingly.

Ways to Lower The pH in Your Freshwater Aquarium

Now let’s look at 7 ways you can successfully lower the ph in your fish tank.

Lower pH in Aquarium with Vinegar

Can vinegar be used in a fish aquarium?

The short answer is YES.

However, when using vinegar in a fish tank, it’s important to understand how it affects your water chemistry.

You see, a high ph means your water has a lot of dissolved basic or alkaline mineral constituents that place your ph reading above 7.

Therefore, anything that has a lower ph, meaning its more acidic, can be used to bring the ph to below neutral; if it’s useable in a fish tank.

Diluted white vinegar is best for use in an aquarium.

Wine and apple cider vinegar can contain other organic elements that are not particularly safe to fish.

When acetic acid in vinegar combines with oxygen in the tank water, it converts to C02, water, and bicarbonate. The increased Co2, in turn, reduces the ph in your aquarium.

It’s recommended using not more than 1ml of vinegar per gallon of water. Also, increase water movement in your tank to make sure the solution spread evenly across the aquarium.

That being said, vinegar is only a temporary fix since for you to keep the ph stable, you would have to add the diluted solution continually.

Plus using natural remedies are safer than vinegar and other chemical solutions. If you accidentally, add a drop too much or a concentration too high you will toxify your fish tank.

Add Peat Moss to Naturally Lower The pH

Adding peat moss is considered one of the most effective and safe ways to lower an aquarium pH. Plus it’s readily available in most pet stores.

However, make sure the product you purchase a brand rated for use in freshwater fish tanks and does not contain chemicals that are harmful to fish or aquatic plants.

There are two ways you can use peat moss in your aquarium, either by placing the soaked product in your aquarium directly, or place the product in a separate aerated container filled with tap water then use that water during your water change.

I recommend you do the changes with peat moss treated water as opposed to adding it directly. This will ensure your water ph remains relatively stable with no erratic fluctuations.

It’s also not uncommon for some aquarists to place peat moss in filters in the form of pellets or small chunks. Still, others float it in the water inside a filter bag or pantyhose.

The only major drawback with peat moss is it’ll discolor your aquarium water. But the coloration is associated with tannins which are responsible for lowering your fish tank ph, hence pretty much a necessary evil.

So how does peat moss work?

When introduced in the aquarium, peat moss releases tannic and gallic acids which attack basic minerals in the water, reducing its hardness and pH.

Use 1 or 2 Pieces of Driftwood

This method works almost the same way as peat moss. Driftwood releases tannic acid in the water which naturally lowers the ph in your aquarium.

You could use whichever size of driftwood that fit in your tank, but I’d recommend one piece for a small tank like a 10-gallon, and two spread out pieces for bigger tanks. This will make sure your fish tank ph is evenly lowered.

When choosing your driftwood, you’ll want to buy one made for use in fish tanks with no dye, chemicals or preservatives.

You can either buy the product in your local pet store or online.

Like peat moss, driftwood can end up coloring your water if you put it directly in your tank. So, avoid this by first soaking the driftwood pieces in water for one to two weeks or boil it for 5 minutes before introducing them in your aquarium.

Boiling is usually a better option since it’ll both reduce the coloration and sterilize the driftwood removing any toxic dirt stuck on there.

Use Almond Leaves

What are almond leaves?

These are leaves of the Terminalia Catappa trees and are also called Indian almond leaves. This tree species is found in a vast area in Asia, the leaves are simply harvested and dried then used in aquariums.

Much like driftwood or peat moss, almond leaves help to naturally lower the pH levels in your tank by releasing tannic acids. They also look nice hence also decorate your fish tank and provide hiding spots for your shy fish.

Almond leaves are available in pet stores and online and mostly come dry packaged in strips; they cost anywhere from $6 to $18.

Simply soak almond leaves in your fish tank, they’ll release tannic acid into the water and gradually lower the ph. The leaves will also add a yellow hue from the tannins, the same as driftwood and peat moss, which may even turn out to be attractive.

Ideally, almond leaves should be placed at the bottom of the tank instead of floating on the water. There they’ll be more effective, add zeal to your substrate and complement other decorations.

The leaves are fairly a long term solution, but you should replace them after six months to a year or whenever they stop having the desired effect. Also when they lose their zeal and are no longer attractive.

Add a Reverse Osmosis Filter

A reverse osmosis filter uses a semi-permeable membrane to purify your aquarium water. The filter works to remove minerals that would otherwise spike your aquarium ph.

RO filter units are the most efficient and long term solution to your high aquarium ph, especially in larger fish tanks albeit a little more expensive than other solutions.

With an RO filter, you can be sure your aquarium ph will not only be lowered but kept stable.

However, since these units are quite expensive, I’d recommend them if you have hard tap water, and you don’t have much time to keep adjusting the ph levels in your tank manually.

RO filters costs usually increase with size and filtration stages, but mostly they range from $200 to $400.

Two-stage units are ideal for smaller tanks while three and four-stage units are better in bigger tanks.

How to Keep Your Aquarium ph Low and Stable

Once you’ve managed to lower your aquarium ph, you will need to keep it stable around neutral or lower if you have fish that prefer slightly acidic water.

That being said, let’s see some proactive measure you can use to successfully keep the ph low and stable.

Clean and Maintain Your Fishtank

Ammonia buildup in water can raise the ph level too high. And though this can be remedied with a biological filter, nitrates, and phosphates from excess waste are also a cause for concern.

Therefore, to stay ahead of these toxic elements, clean your tank every one or two weeks and replace 10 to 20 percent of your aquarium water with clean tap water in five days intervals.

However, before using water from public supplies, check the mineral content and if it’s too hard, consider using remineralized RO water.

Request your local water supplier for the water content analysis report if you are not sure how hard the tap water is.

When cleaning your tank, remember to vacuum the substrate because it plays a crucial role in aquarium water ph. Use a siphon kit to remove grime from the gravel.

Check Your Filters Regularly and Keep them Clean

Occasionally, grime sometimes even fish and plant debris will get sucked into filter inlets. So if you leave the filter uncleaned for long, they will underperform or even fail altogether.

Your filters should generally not appear clogged or dirty, any element that is not part of the filter should be removed.

How you clean your aquarium filter will depend on the type you have. You only need to make sure you get every part that may cause the filter to underperform includes inlets, outlets, and the filter media.

Put simply, remove the components of the filter one at a time as shown in the product manual and in such a way it’s easy for you to put it back together.

Clean each part properly and rinse them under cool running water to remove any sticky grime. Then replace worn out sponges, cartridges, and carbon packets in the filter.

My Two Cents

Test the ph in your aquarium regularly, at least twice every month. Then learn the normal for your tank, this way you’ll easily tell when there is an abnormal spike.

Try to keep your aquarium ph to the average of all your tank inhabitant especially if you have a community tank. In a type tank, stay within the preferred level of the fish you have.

Also, instead of manually trying to lower the ph in your tank, add fish and plants that can handle high alkalinity, ph, and hard water, this includes guppies and Anubias plants.

When your aquarium ph spike is fairly low, use temporary measures like adding driftwood or vinegar but if you have a consistent problem, invest in a reverse osmosis filter.

Enjoy your fish tank.

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