Maintaining Proper Water Quality in the Home Aquarium

Maintaining water quality is fundamental to aquarium fish health. Aquarium hobbyists are faced with the unique challenge of maintaining an aquatic environment capable of sustaining life. Poor water quality creates stressful and toxic conditions that weaken even robust fish. Improper growth, lack of coloration, susceptibility to disease, and other fish health issues may result without stable, healthy water conditions. Aquarium additives and conditioners are a convenient way to achieve proper water parameters and maintain fish health.

An aquarium is an artificial environment requiring intervention from the hobbyist. Without hobbyist involvement, especially during the initial setup period, it is difficult to ensure water quality. Since water used for your aquarium may contain chemicals harmful to aquarium inhabitants, attention to water quality begins at the source. In addition to toxic chlorine and chloramine, your source water may also contain nitrate, phosphate, iron, calcium, silicate, and other chemicals in varying quantity. While your water may be suitable for drinking, it may not be ideal for aquarium use.

Ensuring appropriate water parameters and environmental requirements is fundamental to reduce tank mortality. Following tables are provided as a general guideline and not written in stone. Fish bred in captivity are a lot more hardier and tend to survive in several conditions.

Freshwater Parameters

The following table provides acceptable water parameter ranges for different types of freshwater aquariums, brackish water aquariums, and ponds. The water parameters listed serve as a general guideline for maintaining each specific type of aquarium or pond. Some species of fish, plants, or invertebrates may have more specific requirements, so please review each individual species description for more information.

ParameterFreshwater Community African CichlidsFreshwater Plants & DiscusBrackishPond
Temperature ( ° F )72 - 8272 - 8276 - 8672 - 8233 - 86
pH6.5 - 7.57.8 - 8.56.0 - 7.57.5 - 8.46.5 - 7.5
Ammonia (NH3)
Nitrite (NO2)
Nitrate - Nitrogen (NO3)
Alkalinity (Carbonate Hardness) ( KH )4 - 8 10 - 183 - 810 - 184 - 8
General Hardness ( GH )4 - 12 12 - 203 - 812 - 204 - 12

Marine Parameters

The following chart is a general guideline of acceptable water parameter ranges for different types of tropical marine aquariums. Some types of displays such as FOWLR (Fish Only With Live Rock) aquariums have a broader range of parameters than a reef aquarium. This is due to the delicate nature of corals and invertebrates that are commonly maintained in a reef aquarium. Some species of fish, plants, or invertebrates may have special requirements, so please review each individual species description for more specific information. For reference we have also provided the average water conditions measured on tropical coral reefs across the world.

ParameterSuggested Level:
Reef Aquarium
Suggested Level:
FOWLR Aquarium
Average Level:
Coral Reefs
Specific Gravity1.023 - 1.0251.020 - 1.0251.025
Temperature ( ° F )72 - 7872 - 7882
pH8.1 - 8.48.1 - 8.48.0 - 8.5
Alkalinity ( dKH )8 - 128 - 126 - 8
Ammonia (NH3)UndetectableUndetectableNear Zero
Nitrite (NO2)UndetectableUndetectableNear Zero
Nitrate - Nitrogen (NO3) ( ppm )0.25
Phosphate (PO4) ( ppm )0.13
Calcium ( ppm )350 - 450350 - 450380 - 420
Magnesium ( ppm )1250 - 13501150 - 13501300
Iodine ( ppm )0.06 - 0.100.04 - 0.100.06
Strontium ( ppm )8 - 144 - 108 - 10

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