5 Symptoms Of High pH In Fish Tanks (& 5 Solutions)

When your tank has a high pH (hydrogen), it has too much acid. There can be many symptoms that can give you a heads-up to let you know that something is wrong. So, what are the main symptoms associated with high pH levels in your fish tank?

High pH levels in the tank will cause fish to show excessive excitement, scratching, and trying to jump out of the tank. If the problem is not solved, they will start showing signs of disease, such as white spots on the body and bloody fins, which are signs of ich.

Your fish will look like they have lost their minds at first, zipping across the tank like they were on a mission. But if left too long, the issues could cause fatalities, especially if you do not get the ich treated promptly.

Symptoms Of High pH In Fish Tanks

High pH levels can be good for some fish, such as Cichlids, but they can be deadly for others. You must adjust the pH to match your fish and maintain stable levels. Fluctuations in the acidic levels are what cause the problems.

Fish Gills Are Damaged By High pH Levels

Fish gills can be compared to your lungs. They allow the fish to breathe, but unlike us, they are designed to live in water. If the pH levels jump, the gills will become damaged, making it hard for the fish to breathe.

Skin On The Fish Will Become Damaged

The mucus located within the skin will become damaged. This mucus protects the skin from moisture, which is why the skin on the fish will become damaged and start rotting away.

Fins On The Fish Will Deteriorate

High pH levels will cause damage to the fins of the fish, which is easily seen on the bigger fins around the tail and the top of the back.

image of amano (Yamato) shrimp and ember tetra fish in aquarium tank with a variety of aquatic plants inside by nature style concept.

High pH Can Cause Ammonia Toxicity

It sounds as bad as it is. Fish cannot breathe ammonia through their gills, so your tank will crash if this occurs. You can check this by using your pH test strips, which you should use regularly. That is the best way to catch changes to your tank before it reaches this stage.

Algae Growth Will Increase Dramatically

Algae is not a bad thing, especially when you have some fish that love to feast on it, such as an algae eater. The problem is when the algae growth suddenly increases, causing your tank to turn green within a couple of days. That is when you know that you have a problem.

What Causes High pH In Your Aquarium

There are a few common causes of high pH levels in your fish tank. You must remember that life within your aquarium is delicate, and they need constant care and supervision to maintain good health.

Calcium-Rich Decorations Can Cause High pH

One of the most common causes of high pH levels is the ornaments you buy off the shelf. They are loaded with calcium, which is a mineral that raises the amount of pH in the water.

Low CO2 Causes Low pH

Low pH is not as dangerous as high levels but can still cause havoc in your tank. The more aeration you have going into the tank, the less CO2 you will have in the water. When this happens, the pH will drop.

Using Tap Water Is A Common Cause Of pH Fluctuations

Tap water is something you should avoid using at all times when it comes to the water in your fish tank because it can cause a drastic increase in the pH levels. Always use distilled water when filling or adding water to your aquarium.

Old Filters Can Cause High pH Levels

Even if you think the filters still look good, change them regularly. The back of the box should tell you the suggested length of use of the filter you have, so make sure that you follow the manufacturer’s suggestions.

Symptoms Of High pH In Your Fish Tank

High pH levels in your tank can be deadly to the fish that you have in it. The higher levels of acid will cause the fish and any live plants you have to become sickly. Let’s check out the circumstances of higher-than-normal pH levels a little more in-depth.

High pH Levels Cause Excessive Algae Growth

A sure sign that your pH levels are off will be excessive growth of algae on the sides of the tank and on any ornaments and fake plants you have placed inside the tank.

High pH Levels Cause Mild Changes In Fish Behaviors

Your fish will start acting erratically when the pH levels rise above normal. They will dart back and forth throughout the tank, stopping only to scratch on the closest object or to try and jump out of the tank to their death.

Excessive pH Levels Cause Severe Changes In Fish

If you miss the first signs of high pH, the tank will continue to become more acidic. The fish within will start to act sluggish and have difficulty breathing. The fins will begin to spread out, and the gills may start to secrete mucus.

Disease Sets In With Increasing pH Levels

The next stage in the downfall of your tank will be when the fish contract ich. The fish will continue to scratch along the tank’s sides, forming white spots on their bodies. Their fins will start to decay and become bloody.

Death Is The Final Stage Of High pH

It may be too late when your fish show signs of ich. You can treat the disease with some medicine and get the pH levels under control, but if the fish are too far gone, they will end up belly up in your tank, dying from skin disease and the lack of breathing.

How Do I Lower the pH In My Aquarium Quickly?

Lowering the pH quickly can mean the difference between your fish living or dying. It is not a complex task, especially if you have caught the problem early enough. All it takes is some time and a little bit of knowledge.

Store Bought Chemicals Work Fast To Reduce pH Levels

You can buy many chemicals on the market that will decrease your pH levels quickly and safely. This is just a band-aid, though, because it does nothing to fix the long-term problem unless you constantly spend money to keep it level.

Peat Moss Is A Natural Way To Reduce pH Levels

You can buy a bag of peat moss at any retail outlet. Add a handful to your tank because its acidic properties will counteract the acid in the pH levels, helping keep them down.

Driftwood Can Help Decrease pH Levels

Driftwood can be a beautiful centerpiece in the middle of your tank. It offers hiding places for small and at-risk fish while helping the water keep the pH levels balanced and low.

Almond Leaves

Almond leaves work the same as driftwood, but it also helps fight other kinds of bacteria that your fish may have. It is a great way to add some flare to your tank while helping make the water leveler and safer for the critters.

White Vinegar Is A Solution To High pH

The basic white vinegar that you can pick up at the store, if you do not already have some on hand, will work wonders for the pH of our tank. Add small amounts at first and check the pH after it has had time to circulate. A suggested amount is 0.1 ml at a time until the levels are where you want them.

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Is a pH of 8 Too High For Your Aquarium?

Between 6.8 and 8 pH is where you want the water in your tank to be tested. 8 is the highest you want to ever let your tank get to unless you are keeping all fish that enjoy it a little higher. For most fish, though, keep it at 8 or lower.


Keeping the pH below 8 in your fish tank is the optimal level for most freshwater fish. The main thing is to keep your pH at even levels without much fluctuation. There are things, such as driftwood and white vinegar, that you can add to the tank to get it lower and more stable, which is better than using any store-bought chemicals. Remember that you need to pay attention to the pH levels, check them regularly, and fix any problems before your tank crashes.