Common name: Segmented Worms

Annelida, commonly known as segmented worms, is a diverse phylum that includes over 22,000 species, ranging from terrestrial earthworms to aquatic polychaetes. These creatures are characterized by their segmented bodies, which are divided into ring-like segments called annuli. Each segment contains elements of the nervous, excretory, and circulatory systems, allowing for greater flexibility and mobility.

In the context of marine aquariums, polychaetes are the most relevant group within Annelida. These marine worms are often found in live rock and sand substrates, playing crucial roles in the ecosystem. They contribute to the breakdown of organic material and help maintain a healthy substrate by aerating it and facilitating nutrient cycling. Some species, like the feather duster worms, are popular among aquarists for their decorative appearance and can be intentionally added to tanks for their beauty and ecological benefits.

However, not all annelids are desirable in aquariums. Some, such as the bristle worms, can become pests if their populations grow unchecked. While they are excellent scavengers and help clean up detritus, their bristles can irritate fish and corals, and large populations can indicate overfeeding or other imbalances in the tank.

Annelids are fascinating not only for their ecological roles but also for their regenerative abilities. Many species can regenerate lost segments, which is a subject of scientific interest. For aquarists, understanding the balance of beneficial and potentially problematic annelids is key to maintaining a thriving marine environment.

1. 
   Common name: King Ragworm

   Scientific name: Alitta virens
2. 
   Common name: Social feather duster

   Scientific name: Bispira brunnea
3. 
   Common name: Banded Fanworm

   Scientific name: Bispira melanostigma
4. 
   Common name: Social Feather Duster

   Scientific name: Bispira tricyclia
5. 
   Common name: Feather Duster Worm

   Scientific name: Bispira viola
6. 
   Common name: Twin fan worm

   Scientific name: Bispira volutacornis
7. 
   Common name: Green Spoonworm

   Scientific name: Bonellia viridis
8. Common name: Green Leaf Worm

   Scientific name: Eulalia viridis
9. Common name: Norwegian Sea Worm

   Scientific name: Eunice norvegica
10. Common name: Nebulous Terebellid Worm

    Scientific name: Eupolymnia nebulosa
11. Common name: St. Joseph's Cardinalfish

    Scientific name: Eurato sanctijosephi
12. 
    Common name: Common Fireworm

    Scientific name: Eurythoe complanata
13. Common name: Tangled Tubeworm

    Scientific name: Filograna implexa
14. Common name: Filogranella elatensis

    Scientific name: Filogranella elatensis
15. Common name: Unicorn Worm

    Scientific name: Glycera unicornis
16. 
    Common name: Sponge Worm

    Scientific name: Haplosyllis spongicola
17. 
    Common name: bearded fireworm

    Scientific name: Hermodice carunculata
18. 
    Common name: Scale Worm

    Scientific name: Lepidonotus clava
19. Common name: Medusa Worm

    Scientific name: Loimia medusa
20. 
    Common name: Red Feather Duster

    Scientific name: Myxicola infundibulum
21. Common name: Slender Ragworm

    Scientific name: Nereis pelagica
22. Common name: Clam Worm

    Scientific name: Nereis vexillosa
23. Common name: Oenone fulgida

    Scientific name: Oenone fulgida
24. 
    Common name: Bristle Worm

    Scientific name: Phyllodoce lamelligera
25. 
    Common name: hard tube coco worm

    Scientific name: Protula bispiralis
26. 
    Common name: Mediterranean Fanworm

    Scientific name: Sabella fallax
27. 
    Common name: feather duster

    Scientific name: Sabellastarte magnifica
28. 
    Common name: Indian feather duster worm

    Scientific name: Sabellastarte spectabilis
29. 
    Common name: Coral worm

    Scientific name: Salmacina dysteri
30. 
    Common name: tubeworm

    Scientific name: Serpula vermicularis
31. 
    Common name: Christmas Tree Worm

    Scientific name: Spirobranchus corniculatus
32. 
    Common name: Christmas Tree Worm

    Scientific name: Spirobranchus giganteus