Guide to Common Hitchhikers in Reef Tanks
by @A Young reefer

The purpose of this thread is to hopefully assist hobbyists in obtaining the correct id and method of treatment to common hitchhikers. Both; the good ones and the bad ones.

1) Anemones
Some times called the flowers of the sea, many hobbyists keep them intentionally for their striking colors and their one of a kind symbiotic relationship with clownfish.
However not all species of anemones are wanted in reef aquariums like the following ones:

- Aiptasia:
Aiptasia also know as Glass, Rock, Tube, or Glass Rose anemones, have the ability to rapidly multiply and compete other tank inhabitants for food and space aggressively by their capability of stinging their neighbors and harming them. They come in different colors; some are transparent, while others are mostly light brown or tan in color.

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methods of removal:
Do NOT try to scrape, puncture, cut or pull the Aiptasia etc.. inside the tank. this will only cause it to release “spores” into the water column and you will end up with more.
Chemical methods include: Red Sea's Aiptasia X, Frank's F Aiptasia and kalk paste (calcium hydroxide).
fish and inverts that eat Aiptasia: Peppermint shrimp, Aiptasia eating file fish, Aiptasia eating Berghia Nudibranchs and copper band butterfly fish in large enough tanks. However peppermint shrimp are considered as the most risk and hassle free option.
If possible pull the rock or frag out of the tank and scrape it off, then cover the infected are with kalk paste.

-Ball anemones:
Don't let the name fool you! these are actually not anemones but a form of mushroom corals. The majority of people agree that they are not harmful but a cool addition to a reef tank. They come in several colors; white, orange and purple.
In some occasions they tend to sting neighboring corals and eat small inverts like bristle worms and small snails, which are two things that could be commonly observed in corals.
They don't tend to multiply as fast as Aiptasia, if nutrients are kept in check you should not encounter an "infestation" of them.

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Methods of removal if needed:
kalk paste and copper band butterfly fish tend to eat them.

- Majano anemones:
like Aiptasia, Majano anemones can multiply quickly and sting neighboring corals. They have a greenish brown color.

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Methods of removal:
when removing try to disturb them as least as possible to avoid them from releasing "spores" and causing them to multiply.
-kalk paste (calcium hydroxide), Aiptasia X.
- peppermint shrimp sometimes pick on them, but its not guaranteed. Aiptasia eating Filefish are know to eat them however they are not 100% reef safe they are known to nip at clams, zoanthids, and mushrooms.

2) Snails and limpets
considered as one of the most important members of a reef tanks clean up crew, snails come in all shapes and sizes that eat different types of algae. however some are not introduced to a reef tank intentionally.

- Vermited snails:
This a whole taxonomic family called Vermetidae. which consists of over 160 different species. However this is irrelevant when it comes to identifying and eliminating them.
they can be identified by their unique and strange looking tubular shells. They are filter feeders that release a mucus net into the water column to catch food particles. This mucus tent can smother neighboring corals when they feed which will eventually kill the coral.

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Methods of removal:
Keeping nutrients in check will keep their numbers under control, gluing the opening of their tube will prevent them from releasing their food web and eventually killing them. also bumble bee snails are an excellent addition to an clean up crew that will also eat vermited snails.

- Collonista snails:
these tiny snails are a good clean up crew member that graze on algae and do not harm anything. they can reproduce quickly and explode in numbers if conditions are favorable. hence keeping algae under control would keep their numbers in check.

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Sundial Snails:

Often confused with Collonista snails, Sundial snails normally have a black and white pattern. They eat zoas. Manual removal and larger Wrasses that go after snails are your best options.

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- Stomatella snails:
Another great CUC member that feeds on a variety of algae, does not bother anything.

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-Limpets and fleshy limpets:
Great algae grazers that do not harm anything.

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-Chitons:
Great algae eaters, harmless.

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3) Worms and Flat Worms
Here we enter the creepy side of reef keeping, don't let the looks trick you some of these are not as bad as they look!

-Bristle worms including fire worms:
There are many different species falling under the title of "bristle worms". Both good types and bad ones. All fire worms are bristle worms but not all bristle worms are fire worms.
We will be referring to the good ones as bristle worms and the bad ones as fire worms.
-Bristle worms (the good type) generally do not harm anything in your reef tank, in fact they are the complete opposite. They are an excellent clean up crew member, that feeds on detritus and dead matter. avoiding overfeeding keeps their numbers in check.
These can be identified by their relatively thin, gray hued bodies and evenly spaced bright white blisters.

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-Fire worms (bad guys) these can turn your favorite corals into a snack and on the rare occasion eat your fish. And they are known to reproduce rapidly, as a result removing them is highly advised.
They can be identified by their thick bodies with red, yellow, brown or green gill filaments along its body. Moreover, their bristles have a reddish base color with white tips that look like a make up brush. These stinging blisters are toxic and are certainly painful. So avoid touching them at all costs, if stung place the affected area in warm vinegar and allow the bristle to dissolve.

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Method of removal: Halichores wrasses like the yellow wrasse and Melanurus wrasse eat both bristle and fire worms. Arrow crabs eat them however they are known to nibble on soft coral polyps and occasionally eat small slow moving fish. Bristle worm traps also work.

Bobbit Worms:
The nightmare of nightmares...
These can grow to a massive size and hunt your fish and eat your corals.
Method of removal: pull the rock they are living in and get them out, do not cut them into multiple body segments their cut body segment can generate a head.

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-Spaghetti worms:
These critters are usually found living in tubes under the sand that extend a web of tentacles to collect food particles and detritus. They are harmless and don't harm anything.

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-Feather duster fan worms:
Usually confused with hydroids and Aiptasia These beautiful harmless filter feeders come in all different colors. They live in a tube that they extend from to filter feed with a magnificent crown made of feather like strands where they get their name from. Controlled coral feeding keeps their numbers in check.

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-Spirorbid Worms:
Spirorbid Worms are tiny harmless filter feeders. They live in a hard spiral shell that they pop out from to feed similar to a feather duster. They grow on the glass and on rocks, avoiding over feeding keeps their numbers under control.

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-Peanut Worms:
They don't reproduce quickly and don't bother anyone. Peanut worms are scavengers and detritus eaters, that do not harm anything in your tank.

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-Spionid Worms:
These worms build tubes made of sand grains and mucus. They have two white clear palps that stick out from the top of the tube, they are used to grab food particles. These palps can irritate corals.
Methods of removal: you can glue their tubes, 6 line wrasses and Coral banded shrimp show interest in them.

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-Medusa worms:
The Medusa Worm is actually a sea cucumber. They are beneficial particle feeders despite their appearance.

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-Polyclad Flatworm:

Harmful critters that will go after snails and claims. removing them involves dipping them in Bayer and brushing their eggs off of infected areas.

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-Acropora Eating Flatworm:

The name gives it all away. Bayer dips help eradicating them and brush off the eggs. Halichoeres and Leopard wrasses would eat them. camel shrimps would eat any eggs in the tank.

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-Ghost Flatworm:

They are not beneficial Nor harmful, they do not harm anything but they do consume copepods.

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-Acoel flatworms:
Doesn't harm anything, however they can quickly increase in numbers.
Method of removal if needed: wrasses from the Halichoeres family like the Melanurus wrasse eat Acoel flatworms.

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-Pumpkin Flatworms:
Characterized by having a pumpkin silhouette and a yellow dot. these little buggers tend to smother the coral depriving it of light and flow, which will eventually lead to the death of the coral. Manual removal and a Halichoeres wrasse are your best options.

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-Red Planaria Flatworm:
similar to the pumpkin flatworms they can reproduce at an astonishing rate and smother your corals.
Melanurus wrasses and blue velvet nudibranchs will eat them. Coral banded shrimp are also said to eat them.
NOTE: if flatworm exit by Salifert is used or any similar products make sure to siphon any dead worms out of your sand bed, they can release harmful toxins if not removed.

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For flatworms chemical products such as flatworm exit are quite effective against flatworms, however the main concern is that the die off can release harmful toxins and potentially cause a nutrient spike. hence the removal of any dead worms after treatment is very important. a water change after treatment is also advised.

4) Crabs and Shrimp
These somewhat cute little fellas are often little demons in disguise, that can cause havoc in a tank.

-Gorilla crabs:
They are pests that will eat anything they can get their claws on, including small fish, starfish, corals, clams, and shrimp. They can be identified by their hairy body, hairy legs, and black-tipped claws. They can also get quite large.
Method of removal: Since there really is nothing you can add to your tank to remove them. you need to do it by your self and physically remove them. crab traps also work.

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-Good coral crabs:
These crabs will be found living in the branches of the host coral defending the coral from other crabs or predators like starfish. They do not harm the coral, but feed on the mucus produced by the coral.
The following are the most common types:

Red-dotted coral crab (Trapezia cymodoce):

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Hairy coral crab (Cymo andreossyi):

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Blue-Eyed Coral Crab (Cymo quadrilobatus):

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Furry Coral Crab (Cymo melanodactylus):

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Pale face coral crab (Tetralia cinctipes):

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Photo Credit: HANNAH STEWART, UCSB

-Mantis Shrimp:

They range from rainbow to brown in color, depending on the species. Mantis shrimp are very predatory toward fish and other invertebrates. They are known for their powerful punch that can hurt humans or even shatter aquarium glass so proceed with caution. Finding the rock they are living in and removing them is one option, also a trap can work.

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-Pistol Shrimp:

known for their symbiotic relation ship with gobies pistol shrimp are one of the most sought after invertebrates. They can hitchhike and come in live rock. They are known for their loud sonic booms used to catch small pray underwater. They generally do not post a threat to your tank inhabitants hence their would be no reason to remove them.
Method of removal if needed: a trap but it could be quite difficult to catch them.

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5) Sponges
unlike sponge bob not all sponges are square and yellow. They come in all shapes and colors. They do not harm anything and are beneficial filter feeders. If overgrown and start to bother corals; exposing them to air, scraping, brushing or even placing glue on them should work.

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6) Tunicates

These harmless filter feeders are often confused with sponges. They have two openings to filter water in and out.

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7) Starfish

-Asterina Starfish:

few people have reported that they feed on coral. They are generally harmless and feed on waste and algae. They can reproduce very quickly so manual removal or a harlequin shrimp are the two best options to remove them if needed.

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-Brittle Starfish:

A common hitchhiker they will stir up the sand and eat detritus and any uneaten food.

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8) Amphipods, Copepods and Isopods

known as the bugs of the reef. They look weird however they play a vital role in providing a healthy reef ecosystem.
Amphipods are larger than both copepods and isopods in size, they eat any any left over food and also act as a food source for many fish.
copepods and isopods can be observed on the glass when a light source is shone in the dark. They clean the water column and act as a food source for many fish like dragonets, wrasses and many more.

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9) Hydroids
Hydroids are known to sing nearby fish and coral. They are usually observed in the early stages of a tank and then disappear as the tank matures. In the unusual occasion of them not going away on their own; Fenbendazole is a known method used to treat hydroids (follow instructions carefully before using).

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10) Comb Jellies
They are filter feeders that cause no harm, can be removed with a net if not wanted.

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11) Zoanthid & Montipora Nudibranch
The name speaks for itself, Bayer dips will eliminate the adults while eggs need to be brushed off the corals. Wrasses like the melanurus and six line (aggressive) wrasse will eat adults and any eggs in the tank.

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12) Zoanthid spiders
These "spiders" feast on zoas and crawl inside of the polyp as it closes and stay hidden beneath Zoanthid Mucus. As a result traditional dips do not show significant results. best method is to physically remove them using tweezers.

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