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REEF AQUARIUM HITCHHIKER FAQ

The following are photos and information about snails, crabs, algaes and other creatures you may find in your reef aquarium tank. I am searching for more and better pics of some of these critters. If you are a reef aquarium hobbyist and you'd like to donate a photo, please send it to [email protected]. If you have something in your tank that isn't on this page, or if you have a link to a good article, please email me!

 

= you probably want to get rid of it   = congratulations!

STATIONARY CRITTERS:            

AIPTASIA

Aiptasia is a pest anemone that can take over your reef tank if you don't get rid of it. They can be brown, yellow, clear, or a few other colors. If you aren't sure if something is aiptasia, poke it with something. If it sucks into the rock, it is likely aiptasia. If it just folds up, it is probably a harmless polyp. More about aiptasia.

 

BUTTON POLYPS

These polyps are very common hitchhiker corals in a reef aquarium. They come in a variety of colors, but are commonly brown or green.

FEATHER DUSTERS

These little worms are extremely common on live rock in a reef tank. They are beneficial filter feeders. The worm lives in a tube and uses its feathered crown to catch particles from the water. They will retract the crown into the tube when spooked. They can be colonial, as in the photo to the right, or can be individual. They come in a variety of colors. Here's an article with lots of great pics.

 

SPIONID WORMS

These worms also live in tubes, but rather than filter feeding like the dusters, they will grab larger food with their palps (the antenna-looking things). They are good scavengers.

Here's a good article that includes spionids.

 

VERMITID SNAILS

The vermitid snail is yet another critter that lives in a tube. These filter feed by throwing out a mucous "net" to catch food. Most of the time, you won't see the worm but will be wondering what the "spiderwebs" in your tank are. Here's your culprit. They are harmless but can irritate corals if their nets are too close.

 

SPIRORBID WORMS

Little hard white spirals on your rock and aquarium glass causing confusion? When you look real close, do they have little feathers sticking out the end? Congrats, you got yourself some spirorbid worms. These little guys live in their calcareous shells and filter feed. They are harmless additions to your reef.

 

FORAMINIFERANS

These little filter feeders are very common on live rock in a reef tank.

Here's a great article about them.

 

ZOANTHIDS

While some of us pay the big bucks to buy these pretty soft corals, some of you get lucky enough to get them for free. While most hitchhiker zos are brown, colorful ones have been known to sneak in on live rock.

 

MAJANO ANEMONES

These pretty little anemones come with a bad attitude. They can quickly reproduce and will sting anything they come into contact with. Therefore, most reefers choose to eradicate them. Too bad... they really are pretty.

 

COLONIAL HYDROIDS

Hydroids come in many shapes and sizes. If you have something that sorta resembles a feather duster, but not really... look into hydroids. They can pack a mighty sting so it is good not to let them grow next to corals. They can be brown like these, white, pink, or other colors. I have been unable to find a good hydroid article to post, but here is an interesting Q&A on them.

 

DIGITATE HYDROIDS

Digitate hydroids spread quickly and sting anything they touch, making them nasty to have in your reef tank. Too bad as it is cool to watch them bob up and down as they stretch out from the rock. They are white hairlike critters with a bulbous tip which will mostly come out at night.

Digitate Hydroid

 

SPONGES

Something soft and squishy on your rock? It's likely a sponge. They come in a wide variety of colors, shapes, and sizes.

Here's a fantastic article with lots of pics.

 

TUNICATES

Tunicates (or sea squirts) are another filter-feeding hitchhiker. These vase-shaped critters can be clear, purple, orange, or a variety of other colors. I am looking for a good article on these guys as I don't know much about them.

 

BARNACLES

If you see a little raised hole on your rock with feathers quickly going in and out the hole, you've got a barnacle. It is actually a little filter feeding shrimp-like creature that lives in the hole.

 

CRITTERS ON THE MOVE:

AMPHIPODS

Amphipods are little "bugs" you may see scurrying about your live rock - especially after lights out.

These little critters are beneficial scavengers and are very common.

For more info... Amphipods


ISOPODS

Isopods are another group of "bugs". These are mainly predatory, with the most common being the fish munching Cirolanid isopod. They are easy to spot due to their big black eyes.

Watch out... they munch people too. For more info about all types of isopods, click here.

COPEPODS

Copepods, sometimes incorrectly called cocopods (I'm coo-coo for cocopods!) or copods, are often the first hitchhiker noticed in the aquarium. "What are these little white fleas on my glass?" or "I have ANTS" are commonly heard. They are a great supplemental fish food. Here's a great article about them.

MYSID SHRIMP

Lots of people think they have baby shrimp when they see these little fellas scooting about (usually at night).

They dart about quickly and are harmless. They also make good extra fish food. I've seen both red and white/clear ones in my tank.

Here is an article about them and here are instructions on culturing them.


BRISTLEWORMS

"I have a centipede in my aquarium!"

Most bristleworms found in our aquariums are good guys. They scavenge leftover food and help stir the sandbed. Put some pellets in your tank at night and watch the fun with a red flashlight. Wooo-creepy! More info. (OH, don't touch them!)


PEANUT WORMS

Your watching your reef tank at night and the light hits a long striped worm. It retracts back into the rock quickly. What IS that thing?! It's ok, just a friendly nocturnal peanut worm out for a bite. Here is more than you'd really need to know about them.


SPAGHETTI AND HAIR WORMS

You may have some odd hairs squirming about on your sandbed. They may be red, green, brown, or white. They grab food too. Looks like you have hair worms (commonly called spaghetti worms). Read about them here.


FLATWORMS

Flatworms come in many shapes and sizes but there are two types that are very common in aquaria. The first is a small clear flatworm. Imagine a blob of clear jello with a forked tail. These type are usually harmless.

The other ones, the red ones, can reach plague proportions as they reproduce rapidly and smother corals. Products like "Flatworm Exit" help eradicate them. Here is Melev's experience using it, and here is more info on flatworms.


MANTIS SHRIMP

These guys are really common hitchhikers on Florida live rock. You may see him at night, or he may be hiding but you hear his "CLICK CLICK" as he digs in the rock (this could also be a pistol shrimp). As cool as they are, mantis are bad news in your tank. They are predatory and will eat anything they can catch, including your inverts and fish. If you have an extra tank, they are great for a species tank. If you don't, don't kill him. There are lots of people looking for them. Here are a bunch of Mantis FAQ.


LIMPETS

Limpets are little pointy-shelled snail-like creatures. You may find them crawling along your glass or rock. I have a ton of them in my sump. These guys are for the most part good guys but there are some bad types. More info here.


SHIELD LIMPETS

Then there are some very different looking critters that are also limpets. The shield limpets are fleshy black slugs with a white shell hidden in their skin. More info here.


CHITONS

Chitons are new to me as I have never had one. But if you find a potato bug in your reef, you have one. They may graze on your coralline algae or diatoms in your tank. Here's a great FAQ about them.


ASTERINA STARS

You may see little oddly shaped white starfish crawling around on your glass. These are asterina stars. They will split and multiply in your tank. MOST asterinas in our tanks are good guys, but there are some types that munch on coral. Watch them... if they are always on your coral, be wary. If they are cruising your glass, they are probably algae grazers. Here's the FAQ.


MINI BRITTLE STARS

Normally you won't see these guys. You'll just notice a small striped or white arm waving out from a hole in the rock. This is their normal behavior and they rarely come out from the rock. They are harmless in the tank and will reproduce if they have food. The FAQ is here.


COLLONISTA SNAILS

These small algae grazers are nocturnal. You'll notice little white spots on your glass, which upon closer inspection, are tiny checkerboard snails. They will reproduce well and are beneficial. They stay small. The largest one I've seen is about 1/4" across. More info here.


PEPPERMINT SNAILS

These smooth, shiny-shelled guys are also nocturnal but they aren't algae grazers.

They will appear out of nowhere to munch on a dead snail. Creepy, yes, but harmless. There are stories of peppermint snails eating live snails, although I've never seen it.


ASTRAEA SNAILS

This is one type I have in my tank, but there are LOTS of them. They are good guys and algae munchers.

Here are Dr. Shimek's snail articles where you can browse different models of snails.

Grazing snails part 1
Grazing snails part 2
Grazing snails part 3


STOMATELLA VARIA

You may think it is a slug, but take a closer look and you'll see its flat fingernail-like shell. These guys will breed like crazy and are fantastic algae consumers. They also have a lizard-like characteristic - they can drop their "tails" if attacked. First time I picked one up and it came apart, it freaked me out! Here are a few more pics.


COLUMBELLID SNAILS

Sold by IPSF as "Strombus grazers", these are easily my favorite snails. They breed like crazy, eat constantly, and are hardy. If you can get your hands on these guys, I highly recommend them. Info from IPSF.


PYRAMID SNAILS

If you see little white snails hitching a ride on your turbo snail, astraea, or clam, you may have these nasty parasites. They suck the blood of their host until dead! If you have them, pick them off their hosts until gone. They are species-specific and will only go after the same type snail or clam (clam pyramids won't attack snails and vice-versa). Here is a great link from skinz78 on reef-to-reef about removing them from a clam.


SUNDIAL SNAILS

The "trap door" covering their opening is the giveaway sign that you are dealing with a sundial. These critters are zoanthid eaters. The only way to eradicate them safely is manual removal. More photos


AEOLID NUDIBRANCHS

There are lots of aeolids (including the aiptasia-eating berghia - a good guy to have!) but the most common one for us is this guy - a zoanthid predator! They are a pain to get rid of but will mow through your zos if you don't. Great information here.


ACRO CRABS

These little "masked" smooth crabs are common hitchhikers on acropora. They are cute and cause no harm to the coral in my experience. They will wave their claws to grab food from the current and will protect their acro from other inhabitants who'd love to crawl on it. Cool article about the crabs preventing coral death in the South Pacific.


PORCELAIN CRABS

These cute crabs are distinguished by their 3 pair of walking legs and their "fans". They catch food particles and transfer to their mouth. They come in a variety of colors and patterns and are common on TBS and Florida rock.


HAIRY CRABS

Their are many types of hairy crabs. In general, most are bad and opportunistic feeders (other than mithrax which have a smooth body, hairy legs, and "scoop" shaped claws). I am against killing any creatures whenever possible so if you find one of these guys, give him a home in your sump or with a friend or your LFS.


SEA SPIDERS

ACK! A spider in my tank! Yep, and they are bad news too. Get that sucker out of there. Here's more info.


URCHINS

Most urchins we get are mainly harmless. This one goes back and forth on my back wall munching coralline algae. He hasn't made a dent in it either.

Here is some great urchin info, including how to tell good from bad.

ALGAES AND GROWTHS:

VALONIA AKA BUBBLE ALGAE

These shiny bubbles can appear green or black in your reef. Usually when you notice it, it will be a single gleaming sphere. The bad thing about valonia is that it spreads rapidly. Some people have success getting rid of them with emerald crabs. I have found that just carefully removing them with tweezers works. More.


CORALLINE ALGAE

In a new reef tank, your first experience with coralline will probably be on your live rock. You'll see some hard purple, green, or red (or maybe even another color) growth. You may also see some purple dots begin to grow on your glass or on a powerhead. Coralline uses light and calcium to grow. More here.

HAIR ALGAE

This fine quick-growing algae can take over fast. While my tang likes to eat it, some don't. And it can be a pain to find a way to eradicate it. Here is a good guide to keeping it under control.


BRYOPSIS

Another "pest" algae, bryopsis can grow out of control. Unlike hair algae, there aren't a lot of critters we keep that enjoy eating it.

CHAETOMORPHA

Also known as spaghetti algae, chaeto is a wiry algae that grows like a big clump of Brillo pad. It is one of the most highly desirable macro alga for use in refugiums.


CAULERPA

There are many, many types, but the photo is is a common variety found in reef tanks.

It grows along, forming new roots and digging into rock as it goes like bermuda grass. It can be hard to remove from your display once it builds a good root system.

Some people use it as nutrient export in a fuge or sump, but there are good and bad sides to caulerpa. More information can be found here.


GRAPE CAULERPA

A particularly annoying type of macro algae. There is an aquarium store near me that has this algae spread throughout all their tanks. Boy is it ugly.


HALIMEDA

More about halimeda here.


DIATOMS

Brown coating on your sand?

More here.


DINOFLAGELLATES

Bubbly gooey slime on your walls and rocks?

More here.


CYANOBACTERIA

Red slime on your glass, sand, and rocks?

More here.

And a general guide to getting rid of nuisance algae.

And another!


MORE ALGAES

Here is a link that covers some other common reef macro alga.

MLINKS TO OTHER HITCHHIKER GUIDES:

Live Aquaria's Pests Invading the Reef Aquarium Hobby

Melev's Reef

Chuck's Addiction

Atlanta Reef Club Hitchhiker Guide

Reefs.org Hitchhiker FAQ

If we are missing a great resource, if you have a hitchhiker that isn't on this page and would like to add it, or if you have links to great articles about creatures in reef aquariums, please email [email protected]. If you still have questions, visit www.reefcentral.com.