Naughty Marine Snails

Patty here,

There are many snail species available for the marine aquarium hobby, and many of them are beneficial to the aquarium as they perform specific duties aiding in the health and up-keep of the tank. Popular types include ceriths and nassarius, great for sand bed stirring and clean-up, and various Turbo species and other algae eaters like astreas and trochus. For the most part, the majority of the snails you find in shops are there for your aquarium’s benefit. There are also many types of snails for sale that may not be a benefit such as predatory snails, and yet others that may find their way into your reef by hitchhiking on or in live rock or corals that you introduce. I want to introduce some naughty snails, and some really naughty snails you can watch out for to avoid potential issues they may present.

Murex Snails
There are several species of Murex snails that may hitch on rock or collected specimens. Most murex snails are characterized by rough spines or knobs on the shell. They are shaped more like conchs, but are usually rather stout. These are predator snails, and will prey on clams and other bivalves, starfish, and other snails. Some species drill through the shells of their victim to eat the flesh inside the shell. Better safe than sorry with murex snails, remove them to an iso tank or species tank if you want to watch them, they will feed on meaty frozen tidbits if live prey is unavailable.
Tulip Snails, Fasciolaria sp.
Tulip Snails are beautiful creatures, with stunningly banded, smooth shells and a deep pink or red body. These snails are unfortunately carnivores, so they cannot be kept with beneficial snails like turbos and astreas unless you want them to be eaten. They will also prey on bivalves, so no clams, scallops, oysters, or fun little mussles will be around for long if you introduce one of these to your reef either. Tulips are nonetheless offered periodically for sale. They can be kept in the right tank, and are enormously entertaining, but consider their diet before purchasing one. They will feed on bits of frozen mussel, clam, and other meaty foods in the absence of live prey, and can get along with fish and crustaceans that can move away from them.
Flamingo Tongue, Cyphoma sp.
Though these little snails are very pretty, they are not reef safe as they feed only on gorgonians. If you find that one has hitch-hiked on a new specimen, which is not necessarily uncommon, it should be removed from your main reef. They are beautiful specimens, however, for a small species tank. If you have large gorgonian colonies, small pieces can be clipped and place into the species tank to feed the snail.
Black Limpets, Scutus unguis
Most limpet snails are safe and even beneficial in reef aquaria. The Black Limpet will eat algae but also has a tendency to feed on coral tissue, so if seen in a reef, it should be promptly removed before it is able to proliferate. This is a very cool snail, its delicate black mantle may appear to you to be a sea slug, but its white shell is cloaked by the ebony mantel. If you should come across one in your reef, the first challenge is to dislodge it from the rock, which is not an easy task. You may need to remove the rock itself, which may be placed in a small species tank for observation and enjoyment.
Sundial Snails, Helicanthus variegatus
Sundial snails are small button-shaped snails, kind of flat, with a spiraling, checkered shell. The operculum is shaped like a cone. These snails are most commonly seen on Zoanthid polyps, their primary food source. Obviously, these snails can be detrimental to polyp colonies and they should be removed from your reef if you come across them. They hide well amongst polyps and rock, so be sure to keep an eye out, especially when introducing new colonies.
Conchs and Cowries
Just an additional note, there are lots of different cowries and conchs offered in the trade today, and they are some of the most interesting snails you can find. Be responsible as aquarists, and be sure to find out about any species you’re interested in before purchasing them. Most species are safe and functional, but others with size and diet in mind may only be appropriate for large, non-reef homes. Some Cowries can grow to 4 inches or so, and though reef safe, they can easily topple rock and corals in their travels. The Egg Cowry only dines on soft corals. As for Conchs, most offered are marvelous sand sifters like our burrowing conch, but many conchs can grow to be very large and thus disruptive in smaller tanks and tanks with limited sand bed area. Crown conchs, Queen conchs, and many others are omnivores and may prey on bivalves if algae and other foodstuffs are scarce, so be aware of the needs of the snail you purchase.

Until next blog,


Coral Propagation for Beginners

Dave here. Coral propagation, or fragging as we reef geeks refer to it, is the process of creating new coral colonies from a parent colony. Over the last several years, techniques, products, and general knowledge of the practice rapidly evolved to where it is quite common. As little as five years ago it was something new and exciting, or even scary depending upon your perspective. The thought of cutting pieces off of your prized coral colonies may seem intimidating at first, but it is actually quite safe, and the fragment has an excellent chance of survival if properly handled. Some corals are more easily fragged, and are better suited for the beginner, than others.

These types are what I will focus on for this blog. In general branching stony corals, and Zoo polyps, are among the easiest and most desired corals to frag. If you look around for your local reef or aquarium clubs, many of them will have frag swap meets, so that hobbyists can sell and trade frags with other hobbyists. It is a really great way to promote coral conservation: the more fragged corals you keep, the fewer corals need to be collected from the reefs. Frag swapping is also a great way to share knowledge, and increase the survivability of captive corals. Propagated corals are hardier, and often more colorful, than wild corals. They have been raised in artificial conditions, and will usually keep their color. Wild corals can change color dramatically when adjusting to captive conditions.

There are a few basic items that you will need in order to start coral fragging. First, you need a suitable coral (Duh!). You should try to use only healthy coral colonies for fragging, as it will increase the survivability of both the parent and the cutting. While much fragging is done with damaged or dying corals in an attempt to save something, this is a much less successful way to produce coral frags, and should only be done as a last resort for the specimen. Fragging healthy corals will lead to a much better result.
Second, you will need something to mount the coral to, and there are several options here. Live rock rubble makes excellent, natural looking frags, but can be difficult to get in volume, and can be difficult to keep stable while the frag is securing itself. Commercially available Plugs and Disks, while less attractive initially, allow for quick and easy attaching. Using Plugs and Disks will also allow for easy volume production, as they will either fit snugly into egg crate material, or flat surfaces, so that you can grow out many frags, securely, in a small area. While we are on the subject of eggcrate, for those of you unfamiliar with the material, this can be found any home improvement center in the lighting section. Eggcrate can easily be cut and built into shelves and platforms to mount your frags for establishment and growth.
Next, you will need glue for attaching your cuttings to your rubble, plug, or disk. “Super Glue”,or Cyanoacrylate Gel is the glue of choice. This glue is harmless to the coral, dries quickly, and is easy to use. The glue is available in clear and pink colors, as well as different thicknesses for the job at hand. Your other choice is epoxy putty, this works well for some stony corals, and is well suited for use on rubble rock. Epoxy Putty is also available in several colors.

Finally, you will need cutting tools. Several types of cutters, scalpels, and snips are available on the market. Depending upon the type of coral being cut, different tools will work best, so it is best to have an assortment of tools at your disposal. What you may like to use may not be what I like to use, but if it suits your purposes, go for it. In general snips, shears, and cutters should be used on branching stony corals, and scalpels, razors, or chisels work best for Zooanthid polyps and encrusting corals.
You should strongly consider using safety goggles and rubber gloves, as many of the secretions and fluids that are produced when cutting corals can be very irritating, and even dangerous, to your skin and eyes. Protection is very important.

Once you have all the tools you need, the fragging process is easy. For stony coral, it is as simple as cutting the tips off of one or more of the branches of your parent colony and gluing the freshly cut tip to your plug or piece of rubble. Don’t be shy about the amount of glue that you use, you want to make sure that it stays attached so it can grow onto the plug. You can remove the coral from the water to perform this step. The parent colony will heal over and grow a new tip, or tips. The freshly attached frag will, over a period of weeks or months depending on species, grow over the glue and firmly attach to the plug.

Zoo Polyps can be removed from a parent colony by carefully removing them from the rock they are attached to with a scalpel or sharp chisel. Just a few full polyps are all that you need to start a new colony. With each removed polyp, a new frag colony can be started. Attach the cut polyp to a disk or piece of rubble rock, and then the polyp will attach and multiply on its own. Just as with the stony coral frag, the zoo polyp frag will grow over the glue and cover the disk or rock over a period of weeks to months.

This process can be repeated over and over, allowing you to produce many frags over time. Most people will choose to do this with just a few corals, and use these new frags to trade or sell for different species for their displays.

Interested in a more hands-on and guided approach? Stop by a frag swap! That Fish Place – That Pet Place in Lancaster, PA hosts one with the Reef Conservation Society Bi-annually. If you’re not in the area, Googling ‘frag swap’ is sure to yield one near you.

Until next blog


Blue Collar Workers: A tribute to the Manual Laborers of Our Aquariums

Welcome back Patty Little to That Fish Blog.

Labor Day in the U.S. is dedicated to the workers and was originally conceived to celebrate the strength and spirit of trades and labor organizations.  I thought it might be nice to recognize some of the laborers that make the microcosm of the home aquarium successful to keep up with the Labor Day spirit.  They may not get a paycheck, but they give it their all.  Since they can’t enjoy a day off and a barbecue (though some of their relatives may be on it), let’s put on a blog parade for the little guys.

Kudos to the parasite cleaners, cleaner wrasses and cleaner shrimp, whose dedicated services are invaluable to the health of other reef citizens.
Mower BlennyThanks to the cucumbers, gobies, burrowing snails, sifting stars, and others who keep the substrate aerated and algae free, and to the Mower blennies, urchins, hermits, snails and tangs, the gardeners of the tank who keep the algae hedges trimmed and the macro algae forests at bay.
Hats off to the pest control squadron, peppermint shrimp, arrow crabs, flat-worm eaters, and others whom Nature intended to keep those pesky little critters in check.
And we can’t forget those who stay in the shadows, the detritivores.  Though not very attractive, and often downright creepy, they are a key element removing and processing the crud (for lack of a better term) that accumulates from the stuff in our tanks.  Amphipods, bristleworms, scavenger stars, snails, and nematodes to name just a few.
The freshwater community may not appear to be quite as complex, yet there are those who deserve a big pat on the dorsal (or maybe a special treat) today.  The upkeep of a freshwater tank can be attributed to some specific characters in the tank.
Give a nod to the ever cleaning algae eaters, From Otos to Apple snails, their work is never done, scouring the glass, the rocks, and the other furniture tirelessly to keep the green monster under control.
Then there are the bottom feeders, the plecos, loaches, catfish whose lowly yet secure positions can only be replaced by the gravel siphon.
Perhaps the biggest honor should go to the dedicated aquarists out there who work hard with endless enthusiasm for their tanks and the creatures within.  Though it is a “hobby”, and the labor involved is sometimes frustrating, exhausting, and messy, it can pay off when you look at your tank in awe.  So thanks to all of you who dedicate your time and energy to your amazing tanks, to help out the little guys inside and reward everyone who you share it with.  Happy Labor Day (Well, one week later)!


Aquarium Slime: What is it and what to do about it?

“Slime algae” is a common problem with aquarists of all levels but getting rid of it can be tricky. The name “slime algae” is a misnomer and what may looks like a slime in your tank could be a number of different problems or, more commonly, a symptom of a number of different problems. The key to getting rid of it is to identify and eliminate the cause rather than just treating the symptom.

As with most aquarium problems, diagnosing this problem starts with testing your water quality. Water tests are just like vital signs at a doctor’s office and can point to or eliminate a lot of different problems in an aquarium. In addition to the four core water tests – Ammonia,Nitrite, Nitrate, and pH – testing the Phosphate level is also important in algae and algae-like issues like this. We’ll go into more detail later with how each parameter may be causing your problem and how they can be used to solve it.

Next, take a look at the “slime” itself…we’ll use these different appearances to help narrow down which you might be seeing in your tank. What color is the algae – red, green, black, brown, white? What is the texture like – thick and mat-like, a thin coating, wispy, cloudy? Do you notice it growing anywhere particular on the tank – only on the substrate or a certain ornament, in a circulation deadspot, only towards the top? Can it be easily brushed away? Are there bubbles forming beneath it?

Now to the different “slimes”…

Red Cyanobacteria in saltwater tank

Thick and mat-like, usually dark red (especially in saltwater) or dark green (especially in freshwater). Bubbles form underneath the mats and it is easy to brush off of surfaces.

This is the most common “slime algae” that aquarists encounter but it isn’t actually an algae at all even though it may behave like one. This is Cyanobacteria (often simply called “cyano”). Cyanobacteria are bacteria that manufacture their own food and live in colonies — large enough for you to see them! It’s these colonies that cause trouble for aquarists. They are not necessarily blue-green but can be black, green, blue green, and the familiar dark red sheets covering many surfaces in an aquarium.

The first thing aquarists who find an unwanted colony of cyanobacteria in their aquarium want to know is how to get rid of it. Well, this is where it gets tricky. To eradicate the problem, the particular trigger for the cyano bloom must be identified and treated. Not every bloom is in response to the same trigger and while throwing a chemical at the problem will perhaps clear it up temporarily, it will come back, and it will be worse. Cyano has a few common causes:

  • High Nitrates (NO3-)/Dissolved Organic Carbon (DOC): These two parameters go hand-in-hand and are often interchangeable for an aquarist’s purposes. Nitrate and DOC is a food source of the bacterial side of the bacteria-algae. Sources include: fish slime, algae, bacteria, digested/uneaten food, metabolic waste, live food, some aquarium additives etc.
    • Key Appearance: The cyano with this cause will grow fairly indiscriminately anywhere in the tank where it gets light. This is usually the thickest mats of cyano.
    • Solution: This is best done by frequent water changes, good water movement (power heads and closed system circulation ) and (this is important!) a good protein skimmer (for saltwater tanks only). An undersized or ineffective protein skimmer, high waste loads, or a combination thereof will increase the dissolved carbon level. As a rule of thumb for skimmers; buy one that is rated for at least twice the size of your tank. It may take some adjusting but a properly functioning skimmer can remove ½ cup of thick organic scum from a tank a day. Also, watch what you feed. Feed once a day. If you wish to feed twice, simply split the amount in half – don’t feed twice as much food. If you feed grocery store bought seafood or are making your own foods, rinse all foods thoroughly as seafood sold for human consumption is treated with phosphates and preservatives to keep it fresher longer. (It’s true!) Avoid flake foods, these dissolve too fast – pellets and crisps are much better and more palatable.
  • High Phosphates (PO43-): This level is similar to the Nitrates above and may come from some of the same sources. It is used as a preservative in some foods as mentioned, but is usually the result of the water source. If you are using tap water, be sure to test the water before adding it to your tank, especially if it is well water or if you are in an area with a lot of agriculture and run-off. You can also check with your municipality if you use a municipal or “city” water source since Phosphate may not be removed in all areas.
    • Key Appearance: Similar to above.
    • Solution: Frequent water changes with Phosphate-free water. If your water source already has high Phosphate levels before it even makes it to your tank, consider installing an RO/DI (Reverse Osmosis/Deionization) Unit . This filtering system removes all impurities (including Phosphate, Nitrate, and DOC). If you already have an RO/DI Unit, make sure all the membranes are installed correctly and changed regularly. If you aren’t able to install your own unit, many stores like ours sell RO/DI water by the gallon. Filter medias are also available to help remove Phosphates faster than water changes alone.
  • Lighting:The food source for the algal side of the bacteria-algae is light. This is becoming less common as LED lighting is replacing older fluorescent aquarium lighting but if you are still using fluorescent bulbs, check on the age of your bulbs. Light bulb spectra (the “color” of the light) shift as they age, resulting more favorable conditions for photosynthesis to take place more vigorously. Older bulbs become more yellow in color and the “good” plants and algae can’t use this spectrum as well as the “bad” algae and cyano can.
    • Key Appearance: If lighting is the cause, you are most likely to see the cyano forming in the most brightly-lit areas of the tank with the most direct light. Since light wave penetrate differently through the water column, you may see a gradient in the cyano growth from top to bottom.
    • Solution: Replace old bulbs. If your fluorescent bulbs are older than 6-8 months, it is time to replace them. Even if they still “look” bright, the color will have started degrading. If you are able to, consider switching to an LED fixture. In addition to being much more energy efficient, they don’t age and lose their spectrum in the same way fluorescent bulbs will.
  • Poor Circulation: In this case, you may see cyano in only certain areas of the tank like corners or areas sheltered by rockwork. In these areas, the circulation is blocked or can’t reach sufficiently and any waste can build up before it can be removed by the filter. This provides a captive food source for the cyano.
    • Solution: Rearrange your tank or install powerheads or pumps to increase the circulation. Consider upgrading your filter as well if it isn’t powerful enough for the tank size.

Green Cyanobacteria in freshwater tank

Thin and wispy sheets, usually on the substrate and especially in freshwater tanks. Usually green, brown, or blue-green

Trick question! This is also Cyano. This appearance is more common in freshwater tanks and in higher-flow environments where the Cyano can’t settle into thick mats. The same causes and solutions above still apply.

It should also be mentioned that there are chemicals to “treat” Cyano. Cyano is a gram negative (thin cell membrane) bacteria, much like most bacteria in the aquatic environment. A dose of Erythromycin will knock out the colony of slime quite quickly and this is the active ingredient in most Cyano chemicals on the market. However, since the nitrifying bacteria you need in your tank are gram negative as well, they will be affected also, either being killed or severely damaged. This treatment is more advisable in freshwater aquaria, but only with careful attention paid to water quality while treating. Like all antibiotics, if dosed frequently the cyano will develop a resistance. This should be a short-term fix only, and the problem leading to the cyano bloom in the first place still has to be addressed to eliminate it for good.

Diatom Algae in new tank

Thin light brown coating on exposed surfaces, especially in new aquariums (less than 4-6 weeks) or in tanks that have recently been “restarted” with a large water change (over 40-50%), medication, or other event

A few weeks after the tank has started cycling (after live rock, fish or a bacteria culture has been added), you may see a thin brown film covering the surfaces and sides of the tank. This film scrapes or wipes off easily and cutting back lighting doesn’t seem to affect it. No snails, hermit crabs or fish feed on it, but critters moving across the substrate or glass tend to stir it up enough so it “goes away.” So, what is going on at this point?

The “algae” you see is not a type of plant with cells like traditional green algae that most people think of. It is actually made up of diatoms, a type of phytoplankton whose cell walls are primarily made up of the mineral silicate. It blooms towards the end of the cycling process in a tank because of the imbalance of nutrients in the system but will usually die off on its own once the water chemistry in the tank stabilizes. This is what we commonly refer to as “New Tank Syndrome” (NTS).

  • Solution: Just wait! As tricky as it may be, the best tool to combat NTS is patience. Once the cycle progresses and the tank becomes established, this diatom bloom will exhaust itself and fade away on its own. You can clean the sides of the tank and stir up the substrate to break up the algae, but avoid the temptation to do water changes or add any algacides at this point….this will only cause the cycle to take even longer to finish and the NTS will keep coming back. Most tanks take about 4-8 weeks to cycle, depending on the bioload and size of the tank.
  • For more information, see our article Explaining the Nitrogen Cycle.

Fungus on driftwood

White, mold-like coating often isolated to a single ornament (especially natural ornaments like driftwood) in a freshwater tank

This is usually a sign of fungus or decomposition. If the “slime” is translucent in appearance, it is more likely to be a fungal growth. This is common on ornaments that may have been left outside and exposed to airborne spores, or on pieces washed with some detergents. If possible, remove the piece from the aquarium and scrub it thoroughly in a bucket of tank water or under warm running water. Spider Wood especially is notorious for becoming moldy when first added to a tank but will usually dissipate on its own in time.

If the “slime” is more opaque in color and easily brushes away, something is decomposing. If this is a natural material like a once-dried-out starfish or another animal, dispose of it…it will only continue to decompose and harm the water quality. If it is a harder object like a piece of wood, you can try cleaning it like described above but if it continues to soften or fall apart, it likely just isn’t a safe type of wood and should be replaced as well.

These are just a few of the most common “slime”-related issues we encounter often but are far from everything you may experience. We have come across some really unusual circumstances that have turned out to be related to something as seemingly unconnected as an oil-diffuser air freshener in an outlet near the tank. Feel free to let us know if you need help troubleshooting with your own tank!

Originally published September 9, 2008. Updated May 13, 2020.

Brittle Stars, Sea Stars and Sea Urchins – an Introduction to Some Popular Echinoderms

Frank Indiviglio here with an introduction to Echinoderms.

Sea stars, or starfishes, are perhaps the most familiar of the Echinoderms (a phylum containing over 7,000 marine species), and many adapt well to aquarium life.  Most people are quite surprised to realize that they are active, interesting predators that routinely exhibit a wide variety of behaviors in the aquarium.  Many are also useful scavengers, but all are predatory in nature and, depending upon the species, will consume mollusks, coral polyps and other sedentary invertebrates.

Red-knobbed Sea Star, Protoreaster lincki
Red-knobbed Sea StarWhen picturing a sea star, many people think of the simple reddish-orange animal so often seen as a dried curio in beachfront shops.  However, many are fantastic in appearance and coloration.  The Red-knobbed Sea Star, with brick-red dorsal spines set off against a dazzling white background, is a case in point.

Native to the Indo-Pacific region, this perennial aquarium favorite reaches a length of 12 inches and is capable of consuming quite large mollusks.  It is best fed by placing a piece of clam, scallop or mussel directly below the body, although it is quite active and capable of finding food on its own.

Although sea stars are quite adept at sensing and locating food, they respond more slowly than do most fish.  Therefore, they will usually remain hungry in a mixed-species tank unless care is taken to see that food is placed directly below each animal.

Brittle Stars
Black Brittle StarBrittle stars bring the word “bizarre” to mind instantly, even to those well acquainted with the sea’s curiosities.  They react very quickly to the scent of food, and their long, slender arms thrash wildly about as they begin to explore.  It is quite a sight to see a tank housing several of these normally sessile creatures suddenly come to life – the many sinuous arms seem to take on a life of their own, yet the animals glide unerringly toward the source of the odor that aroused them.

Brittle stars are harmless to most other creatures and are extremely valuable scavengers.  Perpetually hungry, their thin arms can get into the tiniest of crevices between coral heads and other places where bits of uneaten food might otherwise go unnoticed.

Sea Urchins
These slow-moving, spiny invertebrates are often encountered in tide pools, and are worldwide in distribution.  The spines of all are effective weapons, and many secrete venoms that are as yet not well-studied.  Hot-water baths seem to assist in alleviating the sting caused by most species, but handle all with extreme care.

With over 800 species identified to date, urchin enthusiasts have much to celebrate.  Many unusual species are commercially available, including the Long-spined Sea Urchin, Diadem antillarum and the Pencil Urchin, Heterocentrotus mammillatus. Both feed primarily upon algae, but will also consume bits of fish and shrimp.  The Long-spined Urchin is armed with extremely sharp spines, much to the chagrin of bathers in tropical waters.  The Pencil Urchin is well named – its spines, less numerous than those of other urchins, are very thick and blunt-ended.

Wave your hand above a captive or wild sea urchin and you will likely be surprised at how quickly the seemingly inert beast responds.  A shadow or object passing overhead is viewed by an urchin as a predator, and all the spines are oriented to face the threat.  Although parrot fish, sea otters and wolf fish are adept at clipping off urchin spines or turning the animals over to expose the soft underbody, the defense is, in general, foolproof.

Despite their slow-moving ways, sea urchins are quite active and seem bent on getting into every possible nook and cranny in their aquarium.  Be sure to check that they do not wedge themselves too tightly into small corners, or tumble backwards into coral and become stuck.

I’ll cover individual species in depth in future articles.  Until then, please write in with your questions and comments.  Thanks, Frank.

You can read more about sea urchins, sea stars and their relatives at: