How To Test pH In An Aquarium & When You Need Too

Last Updated on 2023-10-04

If you’re wondering how to test the pH in your aquarium, don’t worry, this article has you covered! I’ve tested the pH in my aquarium hundreds of times, and honestly it’s a breeze.

While the test kit you use is going to determine the accuract and ease, this article is going to cover everything you need to know! So keep reading to find out!

How Do I Test The Ph Of My Aquarium?

If you have an aquarium, it’s essential to keep the pH level at the right level so that your fish stay healthy and happy. The pH level can affect the growth of plants and the health of your fish. Here is a step-by-step guide to testing your aquarium’s pH.

1. Purchase A pH test kit

While there are paper strips, digital test strips, and liquid test kits, I personally like to use liquid test kits. They strike the perfect balance between price and accuract. I’m currently using the API Master Test Kit and I honestly can’t remember when I bought it. So you know they’re going to last a long time!

API FRESHWATER MASTER TEST KIT 800-Test Freshwater Aquarium Water Master Test Kit, White, Single, Multi-colored
  • Contains one (1) API FRESHWATER MASTER TEST KIT 800-Test Freshwater Aquarium Water Master Test Kit, including 7 bottles of testing solutions, 1 color card and 4 tubes with cap
  • Helps monitor water quality and prevent invisible water problems that can be harmful to fish and cause fish loss
  • Accurately monitors 5 most vital water parameters levels in freshwater aquariums: pH, high range pH, ammonia, nitrite, nitrate
  • Designed for use in freshwater aquariums only
  • Use for weekly monitoring and when water or fish problems appear

2. Add A Few Drops Of Solution To Aquarium Water Sample

After buying a test kit, get a sample of your aquarium’s water and put a few drops in the test tubes that come with it. After mixing, let it sit out for a while to make sure everything is mixed well. There will also be a card that shows you what each color means so you can work out the pH

3. Compare Test Solution Color

Once you’ve given it a bit of time, you’ll be able to compare the color of the liquid in the tank to the color of the liquid test kit. Generally for most fish tanks, you’ll want the color of the water to be a nice green. This is neutral.

If your test strip is blue then it’s too alkaline for a lot of fish, if it’s yellow then it’s too acidic.

Just remember that while most fish need neutral, some prefer acidic or alkaline environments.

How Do You Tell If pH Balance Is Off In Fish Tank?

The health and well-being of your fish and other aquatic pets need to keep the proper pH balance in their tank. Fish can get stressed, sick, or even die if their pH levels aren’t correct. So, it’s vital to know if your fish tank’s pH balance is off. Here are some signs that will help you tell if the pH is off.

1. Unusual Fish Behavior

Fish in the wrong pH level tank are uncomfortable and get irritated, and will begin to show signs of stress. Symptoms include swimming erratically about the tank, becoming listless, struggling to breathe, and losing appetite. Your fish may also grow more territorial or aggressive as a result. Long durations of stress can lower your fish’s resistance to disease.

2. Poor Plant Growth

Most aquariums with plants work best when the pH is between 6.0 and 7.0, which is slightly acidic. They can also adapt to a bit lower or higher pH levels. However, when the pH level is too low or too high, the plants in the aquarium may grow slowly or start to wilt and die.

What I noticed in my tank when it became too alkaline was that algae in the tank began to bloom a lot more rapidly as well. So if you notice algae bloom as well as poor plant growth, you’re most likely dealing with a tank which is too alkaline.

3. Fish Get Sick More Often

If the pH level is off, your fish will always be stressed, weakening their immune system. When this happens, your fish will be more likely to get sick. Also, an alkaline environment is often the cause of ich. This fatal disease causes tiny white spots to appear all over your fish’s body.

When Should I Test My Aquarium pH?

If you are new to keeping fish, it might be hard to know when to test the pH of your aquarium. Keeping the pH level of your tank in check might be a problem because it requires you to stick to a regular routine. So, here are some situations when you should check your aquarium’s pH level.

Generally though, I always check the pH, ammonia, nitrite, and nitrates in a tank once a week. Even if the tank is established, I find testing once a week is a good way of keeping on top of any potential problems.

1. When Setting Up A New Aquarium

When setting up a new aquarium, you should test the pH level to ensure it is within the ideal range for your fish. When cycling a new fish tank, the water chemistry is going to change frequently, so it’s a good idea to keep an eye on the pH and other parameters. Before you put fish in your new fish tank, make sure to test the water parameters.

2. After Water Changes

Whenever you perform a water change, it is important to test the pH level to ensure that it remains within the appropriate range. Your aquarium’s pH will decrease with time. Water changes can affect the pH level in your aquarium, so testing it after a water change is crucial. 

3. Before You Add New Fish

Whenever you add new fish to your aquarium, it is essential to test the pH level. This is because different fish species have different pH requirements, and you want to ensure that the pH level suits the new fish. It’s also important to ask the pet store where you bought the fish what the pH level of the aquarium is.

4. When Adjusting The pH Level

When adjusting the pH level in your aquarium, you should test it before and after the adjustment to ensure that you have achieved the desired pH level. To enable the early discovery of problems, the pH should be checked at least once monthly, but ideally every two weeks or more. Even little pH alterations in your aquarium might harm the health of your fish.

5. When Your Fish Shows Stress Or Disease

If you notice that your fish are exhibiting signs of stress or illness, it may be due to an imbalanced pH level. Testing the pH level can help you identify the problem and take appropriate action because not checking puts your fish at risk for illness. pH shifts are particularly harmful, especially on fries or fish already ill or stressed.

What pH Is Tap Water?

The pH of tap water is usually between 6.5 and 8.5. It can be acidic or alkaline. But there are a lot of things that can change the pH of your tap water. The pH level of your tap water can be affected by where your water comes from, how it is purified, and what minerals are in the water.

There are times when the pH of tap water is not in the neutral range. For example, tap water with a pH above 8.5 may be slightly alkaline in places with many minerals. This is because the minerals in the water, like calcium and magnesium, can help make the water more alkaline.

On the other hand, tap water in places with a lot of pollution may have a pH of around 6.5. The pH level drops when carbon dioxide and other pollutants get into the tap water. However, the pH level of tap water in most cities never drops below 6. This is because of the rules that public water systems have to follow.

What Should The pH Level Be In A Fish Tank

The pH level in your aquarium needs to match what the fish in it needs. Many fish can live in a wide range of pH levels, but most live in an waters where the pH is between 6.5 and 8. Always try to keep your aquarium’s pH level in a range that is good for the fish that live there.

Don’t let the water in your aquarium get too acidic or alkaline because it can cause your fish a lot of stress or even kill them. Putting your fish in water with a pH of less than 4 can be bad for them and often kill them. Too high a pH level is also harmful because ammonia reacts with alkalinity, making the water even more dangerous for fish.

You should ensure the water in your aquarium is at the right level and keep the pH level stable. The stress on a fish’s body from sudden changes in water parameters is so great that most fish don’t live in waters where parameters change quickly over long periods. When the pH level changes rapidly, your fish can get shocked, killing them.

Which pH Test Strips For Aquariums?

As you know, I absolutely love the API Master Test Kit, and that’s what I’d recommend overall, however, it can be quite expensive. If you want some cheaper test strips, then here are my recommended choices.

1. Tetra  6-In-1 EasyStrips

Like other test strips the Tetra 6-in-1 pH testing kit also checks for nitrates, nitrites, hardness, chlorine, alkalinity, and pH levels. Not only are the test strips inexpensive, but they also work quickly and give you a result in about a minute. But the problem is that the pads on the strip may begin to degrade if submerged in water for an extended time. 

Tetra EasyStrips 6-In-1 Aquarium Test Strips, Water Testing 100 Count (Pack of 1)
  • COMPLETE TESTING: Regularly testing your water levels is critical to the success of your aquarium.

2.  API 5-IN-1 Test Strips

This product comes with 25 test strips that can be used in freshwater and saltwater tanks to check pH, nitrite levels, nitrate carbonate, and water hardness. Most of the time, this product works fine, but sometimes the reading on the strip is wrong. The product works well overall and can give consistent readings. 

API 5-IN-1 TEST STRIPS Freshwater and Saltwater Aquarium Test Strips 100-Count Box
  • Contains one (1) API 5-IN-1 TEST STRIPS Freshwater and Saltwater Aquarium Test Strips 100-Count Box

3. SJ WAVE 7 in 1 Aquarium Test Kit

This aquarium testing kit does more than just check the pH level. It also checks for chlorine, water hardness, carbonate hardness, nitrates, and nitrites, which are all very important in fish tanks. It also comes with a thermometer to measure the temperature of the aquarium water. The problem is that some readings are hard to tell what color they are.

SJ WAVE 7 in 1 Aquarium Test Kit for Freshwater Aquarium | Fast & Accurate Water Quality Testing Strips for Aquariums & Ponds | Monitors pH, Hardness, Nitrate, Temperature and More (100 Tests)
  • 𝗖𝗢𝗠𝗣𝗥𝗘𝗛𝗘𝗡𝗦𝗜𝗩𝗘 𝗛𝗢𝗠𝗘 𝗔𝗤𝗨𝗔𝗥𝗜𝗨𝗠 𝗪𝗔𝗧𝗘𝗥 𝗧𝗘𝗦𝗧 𝗞𝗜𝗧 – Ensure the health and well-being of your fish with our Comprehensive Aquarium Test Kit. This all-in-one fish tank test kit is designed to provide convenient, reliable ph test for aquarium and 6 more most critical parameters in fish tanks. Test for pH, Chlorine, General Hardness, Carbonate Hardness, Nitrate, Nitrite, and Temperature, allowing you to have a complete understanding of your aquarium water quality. 6 in 1 Testing strips with aquarium thermometer makes it 7 in 1 Aquarium Test Kit.


The health and happiness of your fish depend on keeping the pH level in your aquarium at the right level. If you want to catch aquarium problems early, you need to test the pH level often with a reliable and accurate pH test kit. Remember that monitoring and taking care of your aquarium regularly are the keys to its success, so remember how important it is to check your pH levels regularly.

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About the author

Hey! I'm Nicolas from Iguane Media !

Blogger and Owner of the betta care fish guide
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