The invertebrates are a large and diverse group of animals that don't have backbones. Pertaining to aquariums, they include animals like crustaceans (shrimp, crabs, lobsters, etc.), molluscs (snails, slugs, nudibranchs, etc.), echinoderms (sea urchins, sea cucumbers), cephalopods (octopi, squids, etc.), cnidarians (corals, anemones, jellyfish), sponges and true worms.
There is a much greater variety of safe invert choices for the saltwater reef aquarium than for freshwater. They live by a wide range of lifestyles; some are sessile (anchored to the bottom) and live by photosynthesis or filter-feeding, while others are relatively active and always searching for food. Some, like sponges, have very simple body plans and live colonially, while some, such as the octopus and the mantis shrimp, are surprisingly complex and intelligent.
Please note that some corals and anemones need strong reef lighting to stay alive because they live with symbiotic algae called zooxanthellae.
Below are some species of invertebrates I have kept in the past or present. I am not trying to make a complete species profile archive of ALL inverts that may be kept in the aquarium, but rather just listing some which I have had personal experience with, and what those experiences were, along with many profile links for further research. Click on the thumbnail photos to see each up close and read more on that species.
Caridina japonica
(Amano Algae Eating Shrimp)
Acropora sp.
(Purple Staghorn Coral)
Anthelia sp.
(Waving Hand Coral)
Capnella sp.
(Kenyan Tree Coral)
Catalaphyllia jardinei
(Elegance Coral)
Caulestrea sp.
(Candy or Trumpet Coral)
Cladiella
(Colt Coral)
Clibanarius tricolor
(Blue-Legged Hermit Crab)
Cucumaria sp.
(Pink & Green Sea Cucumber)
Discosoma sp.
(Blue Mushrooms)
Euphyllia divisa
(Frogspawn)
Fromia milleporella
(Red Indonesian Starfish)
Fungia scutaria
(Plate Coral)
Haliotis sp.
(Tropical Abalone)
Heteractis crispa
(Sebae Anemone)
Hymenocera elegans
(Harlequin Shrimp)
Lima scabra
(Flame Scallop)
Linkia laevigata
(Blue Starfish)
Lophogorgia chilensis
(Red Gorgonian)
Lysmata amboinensis
(Scarlet Skunk Cleaner Shrimp)
Lysmata debelius
(Blood or Fire Shrimp)
Lysmata wurdemanni
(Peppermint Shrimp)
Montipora digitata
Nepthea sp.
(Neon Green Nepthea)
Octopus bimaculatus
(Bimac Octopus)
Odontodactylus scyllarus
(Peacock Mantis Shrimp)
Ophiomyxa sp.
(Serpent Star or Brittlestar)
Palythoa sp.
(Brown Button Polyps)
Parazonathus gracilis
(Yellow Polyps)
Ricordia sp.
(Ricordia Mushrooms)
Sinularia sp.
(Green Finger Coral)
Strombus alatus
(Fighting Conch)
Trachyphyllia geoffroyi
(Green Open Brain)
Tridacna derasa
(Derasa Clam)
Tridacna maxima
(Maxima Clam)
Turbinaria peltata
(Pagoda Coral)
Turbo sp.
(Turbo Snail)
Xenia bali
(Giant Bali Xenia)
Xenia elongata
(Common Pulsing Brown Xenia)
Xenia umbellata
(Pom Pom Xenia)
Zoanthus sp.
(Fiji Orange & Green Polyps)