Things You'll Need
- Calcium test kit
- Magnesium test kit
- Wire brush -- optional
- Distilled or RO water
Instructions
Determine if you even need to test your calcium and magnesium, since the vast majority of aquariums don't need them. You have to worry about these levels only if you keep coral, clams or other invertebrates that absorb calcium. These invertebrates are staples of reef aquariums, but most other aquariums do not need attention to this detail.
Read the manufacturer's instructions carefully. Most work more-or-less the same, but there can be some slight differences between brands.
Obtain a water sample. Most test kits feature glass or plastic vials for collecting water samples. Make sure your vials are clean, since hard water stains can throw off your readings.
Add reagents per the manufacturers' instructions. You may need to shake the bottles of reagents. The directions will specify how many drops of the reagent you need to add.
Cap the vial and shake to mix up the reagent. You may need to let the sample sit for several minutes; read the instructions for your particular kit.
Compare the color of the vial to the color chart that came with the test kit. Hold the vial over a white surface, such as a piece of paper, and look through the top of the vial to get the most accurate reading.
Rinse out the vials and scrub them with a brush. Do not dump the sample back into the aquarium, since reagents can be toxic. Rinse the vials with reverse-osmosis or distilled water.
Repeat your test monthly; test more often if you see signs of problems like invertebrates growing slowly or dying back.