pH - Degree of acidity or alkalinity. Measured from 0pH (extreme acid) to 14pH (extreme alkaline)
Tapwater - between 7.2 - 8 (hard water areas) and 6.6 - 7 (softwater areas)
HARDNESS (DHo): 0 - 3o (soft water) 8-10o (medium hard) 16o plus (very hard)
Often hardness is expressed as 'parts per million' (ppm). 1 ppm = 17.9 DH.More About Hardness
AMMONIA and NITRITE - once biological filter has matured, should be zero readings.
NITRATE - readings will gradually rise due to production by nitrifying bacteria. Keep in check by regular partial water changes.More about the Nitrogen Cycle
PHOSPHATE - Another 'ingredient' of tapwater which, with nitrate, encourages algae growth. Can be removed with RowaPhos(tm)
Specific Gravity (marines only) - 1.020 - 1.024 at 24 degrees C.More About Seawater