Here is a list of some common worms found in a home aquarium. Flatworms, eg AEFW, and worms found on fish, eg flukes, are not included.
1/5 Harm=Minimally harmful, may be visually annnoying
1/5 Use= Minimally useful, filter feeders may help filtration (minimal)
5/5 Harm=Extemely harmful, may hunt fish/may injure you/chemical warfare etc
5/5 Use= Really helpful, cleans really well/reduces algae/eats detritus etc
1. Bristle worm (Common)
Scientific class: Polychaeta
Rarity: Very Common
Food: Plankton and other bits of organic matter such as algae and dead organisms
Harm level: 2/5 Bristles can be painful
Use level: 4/5 Aerate sand and eat detritus
Other: Similar to Fire bristle worms and orange/clam Bristle worms (both seen as worse than common)
Photos:
2. Spirorbis sp.
Scientific class: Polychaeta
Rarity: Very Common
Food: Filter Feeders
Harm level: 1/5
Use level: 1~/5 amy provide boost to filter (if large amount)
Other: N/A
Photos:
3. Spaghetti worm
Scientific Class: Terebellidae
Rarity: Common
Food: Detritus
Harm level: 1/5
Use level: 3/5 Sandbed cleaner and eats detritus
Other: Also called hair worms
Photos:
4. Peanut worm
Scientific class: Sipuncula
Rarity: Common/Uncommon
Food: Detritus
Harm level: 1/5
Use level: 3/5 Sandbed cleaner and eats detritus
Other: Have a little feather part to eat with which can retract.
Photos:
5. Syllidae
Scientific class: Polychaeta
Rarity: Common/Uncommon
Food: Detritus, omnivores/herbivores. May eat sponges.
Harm level: 1/5 No evidence
Use level: 2/5 Sandbed cleaner and eats detritus
Other: N/A
Photos:
6. Spionid/Chaetopterid
Scientific class: Polychaeta
Rarity: Uncommon
Food: Detritus
Harm level: 3/5 Coral boring varities may harm corals
Use level: 0/5 Sorry, not much they can catch with two tentacles
Other: Spinoid/Chaetopterid can't be distiguish except when removed from their tube.
Photos:
7. Feather Duster Worms
Scientific class: Mainly Serpulidae and Sabellidae.
Rarity: Uncommon
Food: Filter feeder
Harm level: 2/5 Can take over a little, but doesnt actually hurt anything. Some fish eat them.
Use level: 3/5 Filter feeder
Other: There are multiple critters considered "featherdusters" in the hobby (Serpulidae, Sabellidae (True feather dusters), Spirorbidae, Sabellaridae). Mainly if it has a tube and has a feathery part to filter feed then it may be considered. This papragraph is about the more typical looking feather dusters which may take over a tank (but not the large ones you could purchase in a store)
Photos:
8.Bobbit worm
Scientific class: Eunicidae
Rarity: Rare
Food: Omnivore, small fish, worms, detritus, macroalgae.
Harm level: 5/5 Will eat your tanks inhabitants. Can get up to ten ft long. Will bite people.
Use level: 0/5 usefullfor people who dont want fish in their tank?
Other: Venomous bristles and sharp mandibles
Photos:
9. Scale worm
Scientific class: Polynoidae
Rarity: Rare
Food: Amphipods, Carnivore, Invertebrates, Zoobenthos
Harm level: 3/5 will eat pods and inverts.
Use level: 1/5
Other: N/A
Photos:
10. Ribbon worm
Scientific Phylum: Nemotid
Rarity: Rare
Food: Carnivores, (annelids, clams and crustaceans) or scavengers.
Harm level: 4/5 some might eat critters in your tank, depends on species and family.
Use level: 2/5 Some eat other worms and scavenge.
Other: Large number or fibbon worms. From what I've seen, usually smoother, fleshier and without obvious segments.
Photos:
Hope you enjoyed! There are more than ten marine worms that exist, but these are some I see more commonly talked about. The photos I took from the web, if anyone wants me to credit them I will!
1/5 Harm=Minimally harmful, may be visually annnoying
1/5 Use= Minimally useful, filter feeders may help filtration (minimal)
5/5 Harm=Extemely harmful, may hunt fish/may injure you/chemical warfare etc
5/5 Use= Really helpful, cleans really well/reduces algae/eats detritus etc
1. Bristle worm (Common)
Scientific class: Polychaeta
Rarity: Very Common
Food: Plankton and other bits of organic matter such as algae and dead organisms
Harm level: 2/5 Bristles can be painful
Use level: 4/5 Aerate sand and eat detritus
Other: Similar to Fire bristle worms and orange/clam Bristle worms (both seen as worse than common)
Photos:
2. Spirorbis sp.
Scientific class: Polychaeta
Rarity: Very Common
Food: Filter Feeders
Harm level: 1/5
Use level: 1~/5 amy provide boost to filter (if large amount)
Other: N/A
Photos:
3. Spaghetti worm
Scientific Class: Terebellidae
Rarity: Common
Food: Detritus
Harm level: 1/5
Use level: 3/5 Sandbed cleaner and eats detritus
Other: Also called hair worms
Photos:
4. Peanut worm
Scientific class: Sipuncula
Rarity: Common/Uncommon
Food: Detritus
Harm level: 1/5
Use level: 3/5 Sandbed cleaner and eats detritus
Other: Have a little feather part to eat with which can retract.
Photos:
5. Syllidae
Scientific class: Polychaeta
Rarity: Common/Uncommon
Food: Detritus, omnivores/herbivores. May eat sponges.
Harm level: 1/5 No evidence
Use level: 2/5 Sandbed cleaner and eats detritus
Other: N/A
Photos:
6. Spionid/Chaetopterid
Scientific class: Polychaeta
Rarity: Uncommon
Food: Detritus
Harm level: 3/5 Coral boring varities may harm corals
Use level: 0/5 Sorry, not much they can catch with two tentacles
Other: Spinoid/Chaetopterid can't be distiguish except when removed from their tube.
Photos:
7. Feather Duster Worms
Scientific class: Mainly Serpulidae and Sabellidae.
Rarity: Uncommon
Food: Filter feeder
Harm level: 2/5 Can take over a little, but doesnt actually hurt anything. Some fish eat them.
Use level: 3/5 Filter feeder
Other: There are multiple critters considered "featherdusters" in the hobby (Serpulidae, Sabellidae (True feather dusters), Spirorbidae, Sabellaridae). Mainly if it has a tube and has a feathery part to filter feed then it may be considered. This papragraph is about the more typical looking feather dusters which may take over a tank (but not the large ones you could purchase in a store)
Photos:
8.Bobbit worm
Scientific class: Eunicidae
Rarity: Rare
Food: Omnivore, small fish, worms, detritus, macroalgae.
Harm level: 5/5 Will eat your tanks inhabitants. Can get up to ten ft long. Will bite people.
Use level: 0/5 usefullfor people who dont want fish in their tank?
Other: Venomous bristles and sharp mandibles
Photos:
9. Scale worm
Scientific class: Polynoidae
Rarity: Rare
Food: Amphipods, Carnivore, Invertebrates, Zoobenthos
Harm level: 3/5 will eat pods and inverts.
Use level: 1/5
Other: N/A
Photos:
10. Ribbon worm
Scientific Phylum: Nemotid
Rarity: Rare
Food: Carnivores, (annelids, clams and crustaceans) or scavengers.
Harm level: 4/5 some might eat critters in your tank, depends on species and family.
Use level: 2/5 Some eat other worms and scavenge.
Other: Large number or fibbon worms. From what I've seen, usually smoother, fleshier and without obvious segments.
Photos:
Hope you enjoyed! There are more than ten marine worms that exist, but these are some I see more commonly talked about. The photos I took from the web, if anyone wants me to credit them I will!