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Gammaridean amphipods - J. C. Fabricius, 1775

Scuds are good fish food and seem to know it, so they are seldom visible during the day. Ron Shimek


Common in most marine tanks with live rock or sand. These highly successful crustaceans lack a carapace. Unlike shrimps, all body segments are visible. Colors vary from colorless to browns or greens. Flattened a bit from side to side. Hindmost visible appendages tend to be longer than the anterior ones, and the terminal segments are splayed out to the side, allowing the animal to stand upright like a bicycle with training wheels. Most in our tanks live by scraping algae off the substrate.

Family: Gammaridae

Other common name(s):

  • Side Shrimps
  • Gammarus Shrimps

Native range:

  • All Seas

Maximum length: 5 cm (2 in)

Minimum aquarium size: 38 L (10 gal)

Lighting: Immaterial.

Water: Marine 24 °C (75 °F) - 28 °C (82 °F)


Aquarium forms are usually detritivores.

Aquarium Compatibility

Harmless; good food for other animals. Easy to raise in a refugium.


They can be cultured in a refugium. Chaetomorpha crassa algae is a good species for amphipod culture, as are the various filamentous green algae referred to as “hair algae.”

Reference: A PocketExpert Guide to Marine Invertebrates
Image credit: RLS
Text credit: RLS