API GH & KH General & Carbonate Hardness Freshwater Aquarium Test Kit
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Duplicate the natural habitat of your freshwater fish and plants and help prevent dangerous pH shifts with API's GH & KH Freshwater Aquarium Test Kit. Water hardness is the amount of dissolved mineral content in water and it comes in two types: general hardness (GH) and carbonate hardness (KH). KH levels can cause rapid and wide shifts in pH levels which can stress fish and cause illness or death. And high levels of GH can create unsightly, calcium crust to form in your aquarium including the hood and glass. To test, just fill a test tube with tank water and add the test drops. The KH value is determine by the amount of test solutions needed to the turn the test water bright yellow. The GH value is determined by the amount of reagent needed to turn the test water green. Then follow the instructions included to take appropriate actions.
Key Benefits- Monitors GH (general hardness) and KH (carbonate hardness) levels for a more natural habitat for your fish.
- Promotes a more natural habitat and is ideal for a planted aquarium.
- Helps prevent wide, abrupt pH level changes from low KH levels.
- Helps fight crusty calcium buildup on the hood and glass of the aquarium.
- Easy to use and comes with everything you need.
(2) liquid dropper bottles with child-resistant safety caps, easy to read instructions with information on how to test and how to correct unsafe water conditions, (2) glass tubes with snap tight caps.
Precautions
HAZARDS TO HUMANS AND ANIMALS: Causes skin irritations. Causes serious eye damage. May cause an allergic skin reaction. May cause respiratory irritation. May cause damage to organs through prolonged or repeated exposure. Do not breathe dust, fume, gas, mist, vapors, spray. Use only in outdoors or in a well-ventilated area. Wear protective gloves, protective clothes, eye protection, face protection. Contaminated work clothing should not be allowed out of the workplace.
FIRST AID: IF IN EYES: Rinse cautiously with water for several minutes. Remove contact lenses, if present and easy to do so. Continue rinsing. Immediately call a poison center, doctor, physician, or first aider. IF ON SKIN: Wash with plenty of water and soap. If skin irritation or rash occurs: get medical advice and attention. Take of contaminated clothing and wash before reuse. IF INHALED: Remove person to fresh air and keep comfortable for breathing. Store locked up. Store in a well ventilated place. Keep container tightly closed. Dispose of contents or container to authorized chemical landfill or if organic to high temperature incineration.
Make your fish feel right at home by softening your hard water with API's Water Softener Pillow.
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Item Number94349
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Aquarium TypeFreshwater
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Fish TypeTropical Freshwater
For Testing KH
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Rinse a clean test tube with water to be tested.
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Fill the test tube with 5 ml of water to be tested (to the line on the tube).
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Holding the bottle vertically, add KH Test Solution, one drop at a time. Be sure to count the number of drops being added.
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Cap the test tube and invert several times after each drop.
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The test is completed when the water in the test tube, after having been shaken, turns from blue to yellow. If you have difficulty discerning the color after the first drop of test solution is added, remove the cap from the test tube and, while holding it over a white background, look down through the tube.
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The KH value is determined by the number of drops of test solution that must be added to turn the water in the test tube bright yellow.
For Testing GH
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Rinse a clean test tube with water to be tested.
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Fill the test tube with 5 ml of water to be tested (to the line on the tube).
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Holding the bottle vertically, add GH Test Solution, one drop at a time. Be sure to count the number of drops being added.
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Cap the test tube and invert several times after each drop.
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The test is completed when the water in the test tube, after having been shaken, turns from orange to green. If you have difficulty discerning the color after the first drop of test solution is added, remove the cap from the test tube and, while holding it over a white background, look down through the tube.
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The GH value is determined by the number of drops of reagent that must be added to turn the water in the test tube green.
What is Carbonate Hardness (KH)?
Carbonate hardness, also known as alkalinity, is the measure of carbonate and bicarbonate concentrations dissolved in water. These minerals are present in municipal, well, and bottled water. The level of carbonate hardness in tap and bottled water depends on the source of the water and the treatment processes it has undergone. Carbonate hardness helps stabilize pH in the aquarium.
An aquarium with a low KH level will tend to be acidic. Aquariums with very low KH are subject to rapid pH shifts if not monitored carefully. Water with a high KH level usually has a high pH.
What is General Hardness (GH)?
General hardness is the measure of calcium and magnesium ion concentrations dissolved in water. These minerals are present in municipal, well, and bottled spring water. The level of general hardness in tap and bottled water depends on the source of the water and the treatment processes it has undergone. Hard water is high in calcium and magnesium, while soft water is low in these minerals.

Fish Care Made Easier
API is a name you can trust when it comes to taking care of fish. Not only are they passionate about fishkeeping, but they're dedicated to improving the hobby and making it easier to maintain the ideal aquatic environment. From helping the novice set up a new tank to providing state-of-the-art filters for advanced systems, you can rely on API's dedication to quality.


Maintain the Perfect Setup
Fishkeeping is a much easier task with API, because they've taken all the guesswork out of setting up a tank and maintaining it. Their proven treatments include water conditioners and clarifiers, fish medications, pH adjusters, algaecides and quick-start solutions—all designed to keep your aquarium crystal clear and your fish happy and healthy.
Testing Is Key
Once you've started a new aquarium, the only way to keep it in perfect balance is with routine water testing. API gives you all the tools you need to create a nurturing environment for both fish and live plants. Their comprehensive Master Test Kits are tailored to freshwater, saltwater or reef environments, and individual tests for things like pH, ammonia or nitrites leave nothing up to chance.


Clearing the Water
API offers reliable three-step filtration for tanks of all sizes with their FILSTAR XP Canister filters and wide variety of filter media. These powerful filters constantly circulate the water, trapping organic waste and odors, removing harmful ammonia and contaminants, and helping good bacteria to thrive in the tank.
Superior Nutrition
Feeding your aquarium inhabitants, whether they're tropical fish, turtles or newts, is something that can be tricky without the right food. API developed a special diet for every type of fish—one that's highly palatable, which leads to less waste in the tank. And that means less ammonia to cloud the water. For your turtle friends, premium floating pellets and stick treats provide multiple vitamins for a stronger, healthier shell.


About API
Through extensive and continuous research and development, API created quality products for all levels of fishkeeping. As people who are passionate about fish care, they understand the rewards of keeping up a successful aquarium or aquarium. With easy-to-read guides and premium treatments, foods, filters and testing equipment, API helps aquarists establish and maintain an environment where fish can flourish.
Customer Reviews
100% Recommend
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14 Reviews
Showing 1-10 of 14 Reviews
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Great item
By Aleviltona on Feb 13, 2021
Easy to use like all the other API items. One of the bottle was leaking and lost about 30% of the fluid. I contacted chewy and they sent a replace within a few hours. Very happy with the website.
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Perfect for trouble shooting problems.
By Demeter on Jun 29, 2020 Top 1000 Contributor
I started having molting issues with my 36gal invert tank. Decided to get the test kit to make sure all was in order. After finding out the GH and KH was just fine I discovered the problem was my liquid fertilizers. It's always good to have test kits around when things start going south.
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unsure of product
By ali7238 on Jun 26, 2020
I can’t tell whether my dkh is just really high or my testings are inaccurate. I also have no use for the gh test.
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Works as described
By Tayler on Jan 11, 2020
This tester works very well. If you need it, get it.
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Good price
By dparker on Jul 30, 2019
This was a good price on this kit. If you need to test for GH and KH you don't have a lot of choice.
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Aquarium water chemistry
By Mango on Feb 10, 2019
This product is outstanding. The reason I rated it 4 stars instead of 5 is because of the nature of the test itself. The results of the test are determined by the number of drops of reagent added to the test tube and the color of the resulting water. The test itself is a judgement. Other water tests are easier to read.
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Testing made Easy
By Halfpint63 on Jan 2, 2019 Top 500 Contributor
Had to purchase this as it wasn't in the API Freshwater Master Test Kit for my Tanks, but my Pond Test Kit has it, CRAZY! Water Hardness affects PH so it has to be tested and this was the only way I could attempt to lower Water Hardness and the PH fluctuations stopped.
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Good product
By Good on Jan 20, 2019
Worked as described, found out my water is a lot harder than originally thought. Not taking steps to reduce the Hardness level
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Works for both fresh & saltwater
By Hudgiebear on Jan 2, 2019
Easy to use & fairly accurate to use as a guide to check alkalinity.
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A must have
By Bonkers on Aug 26, 2018
I wish this came in the Master test kit as this is an absolute necessity for any fish keeper. I guess that's how API makes the bucks and nickle and dimes you.