Fritz General Hardness (GH) Test Kit

The Fritz General Hardness (GH) Test Kit is a liquid reagent test that measures general hardness in freshwater aquariums. It is a drop-count test that reads from 17.9 to 214.8 ppm, and each drop equals 1 dGH (17.9 ppm). See all of our water testing supplies.

What's in the Box

• 1 reagent bottle, 1.25 fl oz (37 mL)
• A test tube
• An instruction card with chart

Why Test General Hardness

Fritz explains that general hardness measures the dissolved minerals calcium and magnesium in your water. These minerals support skeletal development, osmoregulation and enzyme activity in fish, invertebrates and plants. Deficiencies can cause poor growth in fish, molting difficulties in freshwater shrimp and stunted growth in plants, and leaving imbalances unaddressed can lead to stress and disease.

How to Test

1. Fill the test tube to the 5 mL line with aquarium water.
2. Holding the bottle upside down and completely vertical, add one drop at a time. Cap and gently shake the tube between drops, and count each drop.
3. The test is complete when the water turns from yellow or orange to green.
4. The number of drops equals your GH in dGH. Each drop is 17.9 ppm, so 4 drops is 71.6 ppm.

If the color is hard to judge, remove the cap and look down through the tube over a white background.

Keep test solutions out of the aquarium and follow the full instructions in the box.

Reading Your Results

Typical ranges from Fritz:

• Below 4 dGH (0 to 70 ppm): soft water fish such as discus and other South American cichlids
• 4 to 8 dGH (70 to 140 ppm): tropical community fish such as tetras and bettas
• Above 8 dGH (140+ ppm): African Rift Lake cichlids

To raise GH, Fritz recommends Fritz R/O Recharge or Fritz Rift Lake Cichlid Salt. To lower GH, do partial water changes with lower-GH water such as RO/DI.

Specifications

Related Fritz Tests

• Fritz Alkalinity (KH) Test Kit to measure carbonate hardness, which works alongside GH.
• Fritz Wide Range pH Test Kit to check pH.

FAQ

Can I use it in saltwater?
Fritz makes this kit for freshwater aquariums, and the box is labeled for freshwater use.

How do I read the result?
Count the drops it takes to turn the sample from yellow or orange to green. Each drop equals 1 dGH, or 17.9 ppm.