Water hardness in an aquarium refers to the concentration of dissolved minerals in the water, primarily calcium and magnesium ions.
In the aquarium hobby, total hardness is often referred to as general hardness or GH. This measurement is crucial for maintaining a healthy environment for fish, invertebrates, and plants, as different species have specific requirements for the mineral content of their water.
Understanding General Hardness (GH)
General hardness (GH) specifically measures the concentration of divalent cations, mainly calcium (Ca²⁺) and magnesium (Mg²⁺) ions. These are the most common minerals that contribute to water hardness. Other ions can contribute, but calcium and magnesium are the primary focus when discussing GH.
- Why it Matters: These minerals are vital for various biological processes in aquatic life, including osmoregulation, bone and scale development in fish, and shell formation in invertebrates like snails and shrimp.
Measurement Units
GH is commonly measured in two main units:
- Degrees of General Hardness (dGH): This is a traditional unit often used in the aquarium industry. According to the reference, one dGH is equal to 17.9 mg/L or 17.9 ppm.
- Parts Per Million (ppm) or Milligrams Per Liter (mg/L): These units represent the concentration of dissolved minerals by weight. As stated in the reference, 1 ppm is equivalent to 1 mg/L.
Here's a quick conversion based on the reference:
| Unit | Equivalent (ppm or mg/L) |
|---|---|
| 1 dGH | 17.9 ppm (or 17.9 mg/L) |
| 1 ppm | 0.056 dGH |
Note: The reference specifies the conversion for 1 dGH to ppm/mg/L.
How to Measure Aquarium Water Hardness
Aquarists typically measure GH using simple test kits available at pet stores. These kits usually involve adding reagent drops to a water sample until a color change occurs, indicating the GH level in dGH or ppm.
Importance in the Aquarium
Maintaining the correct GH level is essential because different aquatic species originate from diverse natural habitats with varying water chemistries.
- Fish: Some fish, like African cichlids, thrive in hard water (high GH), while others, like Discus or Neon Tetras, prefer soft water (low GH).
- Plants: Many aquatic plants also have GH preferences, affecting their nutrient uptake and growth.
- Invertebrates: Shrimp and snails require sufficient calcium (part of GH) for healthy shell and exoskeleton formation.
Understanding and managing your aquarium's GH is a key part of successful fishkeeping, ensuring the well-being and longevity of its inhabitants.
