Reef Aquarium Parameters

Reef Aquarium Parameters

Keeping proper reef aquarium parameters in check is vital to the success of a beautiful and healthy reef aquarium. We commonly say that the key to keeping a nice aquarium is keeping water parameters within the suggested range. A well-known and highly regarded reef chemist, Randy Holmes Farley, noted the parameters critical to reef keeping and we test these levels in our own tanks and our client’s tanks often.

These listed parameters are for a reef aquarium (a “fish only” system without corals/invertebrates can have slightly different parameters).

For more information on these parameters and what they mean, please visit the original article at

Table 1.  Parameters critical to control in reef aquaria.

Parameter: Reef Aquaria Recommendation: Typical Surface Ocean Value:1
Calcium 380-450 ppm 420 ppm
Alkalinity 2.5-4 meq/L
7-11 dKH
125-200 ppm CaCO3 equivalents
2.5 meq/L
7 dKH
125 ppm CaCO3 equivalents
Salinity 35 ppt
sg = 1.026
34-36 ppt
sg = 1.025-1.027
Temperature 76-83° F Variable2
pH 7.8-8.5 OK
8.1-8.3 is better
8.0-8.3 (can be lower or higher in lagoons)
Magnesium 1250-1350 ppm 1280 ppm
Phosphate < 0.03 ppm 0.005 ppm
Ammonia <0.1 ppm Variable (typically <0.1 ppm)

The following parameters in table 2 play an important part in an aquarium, but not all are required to be tracked, or need to be measured. With regular water changes, most “trace elements” will be replenished.

Table 2.  Other parameters in reef aquaria.

Parameter: Reef Aquaria Recommendation: Typical Ocean Value:1
Silica < 2 ppm, much lower if diatoms are a problem <0.06 – 2.7 ppm
Iodine Control not recommended 0.06 ppm total of all forms
Nitrate < 0.2 ppm Variable (typically below 0.1 ppm)
Nitrite < 0.2 ppm typically Variable (typically below 0.0001 ppm)
Strontium 5-15 ppm 8 ppm
ORP Control not recommended Variable
Boron < 10 ppm 4.4 ppm
Iron Below Kit Detection Limits (additions OK) 0.000006 ppm