Testing you water regularly and knowing the basic parameters and how to keep them stable is essential to a thriving reef aquarium.
When testing your water be sure to follow the instructions carefully and ensure that each drop or measured amount is added accurately.
High grade test kits are also advised since they provide much more accurate readings and serve to cause you much less grief in the long run!
Some reputable brands are: Hanna, Salifert, Nyos, Aqua Forest and RedSea.
You can use a combination of the better brands since some individual tests are much better than the same type of test kit of another brand.
An example of this would be that a Hanna low range phosphate or phosphorus are better than most other brands, but their calcium kits are much less accurate than a Salifert in comparison.
Mixing and matching test kits is common among reef aquarium keepers.
Information provided by:MARINE AQUARIUM FANATICS AUSTRALIA