Marine BioGroups

From Microcosm Aquarium Explorer

CMA Puffer.jpg

Arothron mappa, Map Puffer. Scott W. Michael

Marine: A Definition

Marine is defined "of or pertaining to the ocean or sea," while saltwater is more narrowly defined by aquarists.

The classification of different waters by their salt content, as measured by Specific Gravity (relative density, the most-common measure among aquarists) is:

  • Marine or Saltwater 1.022 – 1.035
  • Brackishwater 1.05 – 1.010
  • Freshwater 1.0

Salinity or salt content is measured as parts per million (ppm) or mg/L:

  • Marine or Saltwater: 3-5% or 30,000-50,000 ppm
  • Brackishwater 0.05-3% or 500-30,000 ppm
  • Freshwater <0.05% or <500 ppm


Marine BioGroups:


Specific Gravity of Different Marine Regions

  • Tropical Indo-Pacific 1.022 – 1.025
  • Caribbean 1.023 – 1.026
  • Red Sea 1.028 – 1.035

Chemical Composition of Seawater

Reference: The Conscientious Marine Aquarist
Image credit: SWM
Text credit: AQG