Common Coral Pests
Sooner or later, all reefkeepers encounter at least one species of common coral pest that hitchhike a ride into their systems when they add a new coral frag or chunk of live rock from a fellow reefer or bought from a brick-and-mortar store or online coral retailer. In most cases, it takes weeks or months for the coralhead to see evidence that they’ve introduced something undesirable to their reef display. By then, rapidly disappearing tissue on a coral colony, a retracting mantle on a prized clam, poor polyp extension or posture or otherwise alarming signs of some kind of infestation are well underway. In our professional opinion, the best defense against these undesirables is:
- A good offense and that begins with strict quarantine protocols
- Careful attention to detail and rigorous inspection of newly acquired frags (even from trusted sources)
- Dipping each new frag in at least two different coral dips before acclimation to your quarantine system
- The removal of frag plugs and other potential hiding places before dipping
- A zero tolerance policy that includes conducting research on the most effective ways to eradicate these soul-crushing and colony-destroying buggers before they wreck your love for reefkeeping
In most cases, these are naturally occurring organisms that have co-evolved with corals over millions of years. They become a problem when they no longer have predators and other natural controls to keep their populations in check. We’re going to briefly discuss a few of these coral pests, how to identify them and some of the ways to deal with them.
Aiptasia Anemones
Also called Glass Rose Anemones, Aiptasia ‘nems are one of the most common scourges of tropical marine systems. Many inexperienced reefers are initially happy to see these anemones waving in the current but that happiness that is short-lived, as they multiply very quickly, outcompete corals for living space and pack a powerful sting that can harm corals, clams and other sessile critters that cannot move away, along with fishes. They reproduce sexually by releasing planula (larvae) into the water. A mature Aiptasia with an oral disc the size of a nickel is capable of releasing dozens of planula every day. They are also capable of reproducing asexually through a process called pedal laceration. They simply tear of a small piece of their pedal base and it grows into a new anemone. As you can see, they have explosive reproductive capacity.
How to Deal with Aiptasia
The best way to keep these anemones from taking over is a zero tolerance policy, where you eradicate them whenever you see them. Manual removal doesn’t work; you’re just helping them reproduce. Your best bet is one of several Aiptasia products on the market. Make sure to buy one that is reef-safe and follow the instructions on the bottle. Be very careful with how you administer these products. They can kill corals, too! Some reefers have experienced success with introducing Berghia nudibranchs to their systems. They are predators of Aiptasia and do work well but can also be eaten by shrimp, crabs and some fish species, especially wrasses.
Majano Anemones
Majano ‘nems are another common pest anemone reefers frequently have to deal with. They tend to be shorter than Aiptasia, with brown, stubby tentacles instead of the long, slender and wispy tentacles and thin stems of Aiptasia. Instead of growing long, Majanos tend to go wide, with some having oral discs as wide as 3cm across. These also have amazing reproductive capacity when food is abundant and they pack a powerful sting that can harm and kill corals, clams, and some fishes.
How to Deal With Majano Anemones
Again, a zero tolerance approach and the use of Aiptasia-controlling products are the way to go here. Berghia nudibranchs won’t eat Majanos but a careful eye, murderous intent and surgical application of a reef-safe product are the best ways to eradicate these critters.
Asterina Sea Stars
Asterina is a genus of sea star with dozens of relatively harmless species that are very common hitchhikers on frags and especially, live rock. Most of the time, they creep around the tank eating biofilm and algae. They can also reproduce fairly rapidly through fragmentation, where they split off one, two or more arms that grow into new stars. This occurs so often that they are frequently misshapen, with only one or two arms present while they regenerate the rest. A few species, however, will eat coral tissue and their reproductive capacity makes them a dangerous coral pest, indeed. At the very least, even the beneficial ones multiply so rapidly that they become unsightly, with dozens on the inside of your glass or acrylic imposing on your view.
How to Deal With Asterina Stars
There really is no easy way to reduce the numbers of Asterina stars except manual removal. This requires steady, daily use of a net to harvest them off the front pane and other easy to get locations. If you’re really dedicated, you can use aquatic tongs to surgically remove them from the rockwork. You’ll never really get them all, it’s impossible, but you can drastically reduce their number and improve the view of your reef. If you’re one of the unfortunate souls with coral-eating Asterina species, you may have to buy a pair of Harlequin Shrimp. They’re quite effective and may be able to eradicate these stars from your system, but they are obligate star eaters and when they run out of stars, they will die. The ethical thing to do would be to purchase a pair and when they make a sizable impact, lend them to a fellow reefer for a while. Everybody wins on that deal. Just make sure you don’t have a fish or inverts that will eat these pretty shrimp!
Pycnogonid Sea Spiders
Pycnogonida is a genus of sea spider with hundreds of different species and only a few have a taste for coral tissue. They tend to be small, spindly-looking arthropods that are easily identifiable as spiders. These critters are an emerging class of reef pests that seems to mostly get imported on corals from Australia. It is not yet fully known if they actually eat coral tissue or just irritate the heck out of colonies. What we do know is that they are primarily nocturnal critters and that’s the best time to go hunting for them.
How to Deal with Pycnogonid Sea Spiders
If you notice that some of the coral frags are starting to be stressed and your water quality is good, consider taking a very careful look at what’s out and about on your coral at night. (It’s a good idea to do this frequently, anyway.) If you see one or more of these spiders, consider adding a wrasse or cleaner shrimp, which are good critters to have in your display and quarantine system. You can also remove them manually with a pipette, baster or, if you’ve a very steady hand, a pair of forceps.
Acropora Red Bugs
Red bugs are a tiny species of crustacean that average about .5mm long. This makes them very difficult to see with the naked eye and most reefers won’t detect an infestation until they see poor or no polyp extension and poor coloration on parts or the whole colony. A closer look usually reveals tiny whitish patches where the red bugs have gnawed on the mucous layer or the tissue itself. With a very careful eye, you may be able to see these crustaceans on the coral.
How to Deal with Acropora Red Bugs
There are a few fish species that may seek out and eat these critters. A six-line wrasse (Pseudocheilinus hexataenia) or other wrasse species, along with Dragonface Pipefish (Corythoichthys haematopterus,) may take a liking to these bugs and eat them but note that we’re using “may eat them” not “will.” Many natural remedies for common reef pests are hit-and-miss. For example, while one Copper-Banded Butterflyfish or Matted Filefish may happily go about eating every Aiptasia in a system, every specimen in a species may not have the same response. From an ethical standpoint, we’re against buying some types of animals for the expressed purpose of removing a reef pest unless the reefer has no other alternative. Particularly if the animals are obligate eaters and will die when they eat the last of the target pests.
Coral-Eating Nudibranchs
There are several species of nudibranch that eat the tissue of soft corals, SPS corals and perhaps even some LPS coral species. So far, we’ve heard of or had to deal with nudibranchs that eat Acropora, Montipora, Zoanthids, Sarcophyton, Palythoas, and a few other coral genera. They have voracious appetites and can quickly devour the thin veneer of living tissue on SPS corals, carve large divots out of leather corals, munch Zoanthid polyps one after another and otherwise wreak havoc on one or more species in your display. In many cases, they will start at an edge and work their way in, leaving clutches of eggs near living tissue so there’s a ready supply of food for emerging larvae. They will also create isolated patches of eaten tissue that look like white spots on a colony, creating a perfect opportunity for secondary bacterial infections to destroy the rest of the colony. This can happen with terrifying speed.
How to Deal With Coral-Eating Nudibranchs
These nudibranchs are difficult to eradicate, particularly if the infestation and reproductive momentum are already out of control. There are some fishes that may eat them but by the time you can find one, it may be too late to save a colony. You can remove the colony and aggressively dip it but it will probably only get the adults. The eggs of these pests are notoriously resistant to coral dips. Moving the affected colony to a quarantine tank and manually removing these buggers one by one may be your best bet but it’s a tedious affair that may or may not save the stressed colony. We wish we had a rosier outlook for dealing with these things. Your mileage may vary.
Brown Flatworms
There are several species of flatworm that hitch rides into reef tanks on frags and live rock but by far the most common are brown flatworms, also called Planaria. Usually, by the time a reefer notices Planaria on coral frags or on the glass above the substrate when the lights come on, an infestation is well underway. These can grow up to .5cm in length but most are usually smaller than that. They (naturally) have explosive reproductive potential and even if they don’t appear to be eating your corals, they pose a significant risk to the system and everything living in it. That’s because when they die, they release a toxin. If a population gets so large that it crashes, you can wake up one morning to see that everything in a display is dead.
How to Deal with Planaria Flatworms
There are some fish species that may eat these flatworms but as we’ve said, they may not. Planaria are photophobic and do not like strong flows, so they tend to come out at night and hang out in low-flow areas of the tank, particularly around the substrate line. Salifert makes a product called Flatworm eXit, which would work well if you remove affected corals and dip them according to directions. You may also use it to dose the whole tank but with the toxin they release after death, there’s an element of risk even if you stage water and tools for a massive water change after the treatment. Some reefers swear by using a siphon made from a piece of airline tubing with a mesh bag tied to one end. They turn off the lights, wait for the Planaria to come out and about and then hoover those buggers from corals and the glass one at a time. It’s tedious, but if you keep up with it you can turn the corner on these pests. We recommend putting the mesh bag in a bucket instead of the sump for toxin control.
Pyramid Snails
If you love Tridacna clams, you’ve probably dealt with or maybe even lost a clam or two to these ruinous little gastropods. Pyramid snails have their name because they belong to the Pyramidellidae family of snails. These snails are quite small; usually 2mm long or less, cone-shaped and mostly invisible until the mantle on a clam begins to recede or the animal ejects its byssal gland and dies. They have a needle-like proboscis that they stick into the tissue of the mantle and suck the fluid and possibly the photosynthetic zooxanthellae out of the tissue. They also attack the delicate tissue of the clam’s byssus. By day, they retreat to the safety of the scutes of the clam’s shell and into the substrate under the clam near the byssal gland. By night, they come out and begin perforating the tissue of the clam, irritating and stressing the animal to death. When they have killed the clams, they will start doing the same thing to the snails of your clean-up crew.
How to Deal with Pyramid Snails
There are some wrasse species that may eat Pyramid snails but they can’t get to the ones under the clam or in the substrate. We’ve had success and saved our beloved clams by removing the clam to a quarantine system with no substrate, putting on an inexpensive dental loupe for magnification, and manually removing the snails with forceps and a toothbrush on a daily basis until they are gone. It’s painstaking work removing them one or a few at a time but immensely satisfying. You’ll also want to assiduously remove the small gelatinous egg masses usually laid in the scutes nearest to the mantle and near the byssus. They like to lay these masses so that hungry larvae don’t have to go far for their first meal after hatching.
Our Pledge to Our Customers
No online coral seller or brick-and-mortar retailer can guarantee that their coral frags are 100% free of these and other common coral pests but we go above and beyond and inspect each frag multiple times to help prevent introducing these pests to your systems. We’ve dealt with most of these pests ourselves and understand how difficult it is to eradicate them once they’re in a reef tank. As we said in the intro, the best defense is a good offense on these buggers and even though we do our very best to ensure each frag is clean, we strongly recommend that you quarantine each frag for at least 30 days and carefully monitor it for signs of hitchhikers. We hope that you never have to deal with these pests but it’s very likely that you will at some point. Life finds a way. The more stringent you are about quarantining all animals before they are introduced to your reef display and observing them carefully, the less likely you are to have to deal with an outbreak that is expensive, heartbreaking and ruinous to your corals and other inverts. For more information on the importance of proper quarantine and biosecurity protocols, please review our Quarantine/Biosecurity page.