Spooky Reef Tank Pests

Reef aquariums certainly take the cake when it comes to creepy crawly pests, most of which either look out of this world or are just plain gross. While these pests are something we suggest you avoid at all costs in your reef aquarium, the odds are you probably have already encountered some of them or are simply counting down the days until you do.  

In most cases, an ounce of prevention is worth a pound of cure but should you find yourself face to face with a bizarre creature that has worn outs it's welcome in your aquarium, here are some tips to help you get your tank back in ship shape. 



The most widely encountered of the reef aquarium scourge, aiptasia are pesky little anemones that spread like wildfire and take no regard for corals or other organisms getting in their way. They sting surrounding invertebrates and bully their way throughout your tank with an incredibly efficient means of reproduction; one aiptasia will turn into 100 seemingly overnight. 

Aiptasia is best addressed right away, at the very first sight in your tank. We like Frank's F-Aiptasia as a topical remedy but you can also call upon some utilitarian animals that actually eat aiptasia. Berghia Nudibranchs are the best because they specialize in aiptasia predation; its the only thing they eat. Peppermint Shrimp, Bristletail Filefish, and Copperband Butterflyfish are also suitable aiptasia eaters but can be hit or miss in terms of how voracious their appetite for anemones might be. 


Bristle Worms & Fireworms

Perhaps the least attractive critter on this list, Bristle Worms and the lesser-known Fireworms are quite horrendous in terms of looks but may actually be beneficial to your reef. How could something so ugly prove to be beneficial?  Well, this actually boils down to the type of worm you have.

The common bristle worms are detritivores and help clean up waste around the aquarium. They pose no threat to your corals or fish, just be careful not to handle them directly for the sake of avoiding the sharp white bristles which can irritate your skin. Fireworms on the other hand are a whole different story because they can prey upon corals and deliver a painful "sting". The good news is that fireworms are far less common hitchhikers and look different enough to easily ID. 

In either case, you can bait and trap these worms for easy removal from your tank. If you're proficient enough with a pair of long metal forceps, capturing them during the evening hours while scavenging your tank is also possible. Some wrasse species will prey upon polychaete worms so adding a Sixline or Radiant Wrasse to your stocking list is a great way to manage these pests naturally.



There are roughly 3,000 unique species of nudibranchs inhabiting our world's oceans and only a handful of these slithering foe wind up causing trouble in our aquariums. As reef aquarists, we are most concerned with the nudibranchs that prey upon coral, specifically Zoanthids, Montipora, and Acropora. Zoa-eating, Monti, and Acropora-eating nudibranchs are pretty common pests among coral collectors and once they inhabit your tank, they reproduce by laying eggs on or near the corals making them difficult to eradicate.

They are tiny, often camouflage really well and only a discerning eye can ID them. Physical removal is the best way to actually get rid of the adults in your tank but the best approach is prevention. Dip and clean ALL of the corals that are placed into your aquarium. Remove new corals from any frag plugs or mounts before gluing them into your aquascape; these mounts are where many of these coral pests hide or lay their eggs. Again, certain species of wrasse have been known to eat nudibranchs but generally speaking may not be the best approach or controlling an active outbreak. 

Digitate HydroidsPhoto Credit: Reef2Reef.com
Colonial HydroidsPhoto Credit: Reef2Reef.com


Not as common as aiptasia but equally as annoying, there are quite a few different types of hydroids with only a few being common in reef tanks. Colonial hydroids and digitate hydroids are both terms used to describe these critters and there really isn't a ton of information on how to properly ID them down to the species level.  In any case, hydroids are very prolific and can pack a sting that can irritate fish, corals, and even your skin.  

The best approach is to remove the rocks and physically remove the hydroids. You can use peroxide to kill them on the surface of the rock and then scrub the rock clean in a container of saltwater. Some hobbyists have had success using Frank's F-Aiptasia in the tank directly for mild infestations. There are also a variety of fish and invertebrates that may eat hydroids including certain urchins, Peppermint Shrimp, nudibranchs, Flame Back Angelfish, and even hermit crabs. 


Red Bugs

Red "Bugs"

While we like to think of "copepods" as beneficial organisms in our reef, there are also harmful copepod species that actually prey upon coral. The most talked about of these predatory copepods are called "red bugs"(tegastes acroporanus) and they infect certain types of Acropora corals. 

The best control is prevention; inspecting, cleaning, and dipping all your new corals is the best way to keep them out of your tank. If they do show up in your display, remove and dip the infected corals using a dog medication called Interceptor which can be obtained from a local veterinarian. This medication contains a broad spectrum anti-parasitic that is very effective in killing these little pods but be careful, the dip must be performed carefully, and rinse the corals really well before placing them back into your tank. It's best to remove the infected corals and set up a little frag tank for isolation where you can observe and treat the corals as needed. Only return the corals to your display when you are confident the bugs are gone. 

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Asterina Starfish

Asterina Starfish

These little starfish tend to stir the pot every now and again because some hobbyists feel they are reef-safe while others do not. Some hobbyists swear they eat corals but more often than not, they never cause a problem and focus on eating detritus and decaying waste. Some of this confusion may be that they are preying upon decaying coral flesh that was damaged otherwise. I have witnessed this firsthand when asterina starfish would congregate around a colony of zoanthids being targeted by zoanthid-eating nudibranchs. They only appeared to prey upon the polyps that were damaged by the nudibranchs. It is also possible that we see different species of asterina show-up, some of which just might have a taste for corals. 

Physical removal is the best way to control them, just pull them out during the evening when they crawl on the glass walls and rocks. In most tanks, they are harmless and shouldn't be of concern unless the population really explodes. In that case, focus on detritus removal and physical removal of the starfish directly. Harlequin Shrimp are awesome-looking shrimp that ONLY eat starfish, something to consider if your tank has a sizable asterina population. 

Vermatid Snails
Vermatid SnailsPhoto Credit: ReefBuilders.com

Vermatid Snails

These stationary gastropods are quite pesky because they not only irritate corals but are extremely difficult to eradicate... at least without tearing your aquascape apart. Vermatids are stationary snails that form a tube-shaped shell that is attached to a rock or inside a coral. They expel a slim that captures planktonic prey and it is that slime that causes all the trouble. This slime irritates coral polyps, causing them to retract and in severe cases can lead to loss of tissue. 

Since Vermatids are stationary, you can easily break the tube off the rock with a sturdy pair of pliers. The problem is, the bottom spiral part of the tube often remains on the rock and is where the actual animal inside will retract when you touch the shell. Therefore, the snail survives and just grows back. You have to ensure you are prying off the entire shell from the rock in order to get rid of them for good.

They will spread throughout your tank and once established, you very well may need to remove the rocks, one by one, and scrape away the snails individually. Bumble Bee snails are known to eat vermatids,  but may not be 100% effective for severe infestations. Using super glue to seal over the top of the tube can also be an effective method to kill the snail inside but can be difficult to accomplish if you have more than just a few. 

Red Planaria FlatwormsPhoto Credit: CoralRX.com

Acropora Eating Flatworms


There are a variety of flatworms that can show up in a reef tank but most often you're going to be concerned with Red Planaria (Rust Brown Flatworms) or Acropora Eating Flatworms. Red Planaria do not prey on coral directly but are quite prolific and can actually cover the surfaces of coral. Acro-eating flatworms are another story and are one of the most dreaded SPS pests because they prey upon the delectable flesh of Acropora. 

Of course, inspect, clean, and dip new corals as a means of prevention and if flatworms do show up, physical removal of the adults is required. For AEFW, remove infected corals, inspect for eggs, remove the eggs, and dip corals to kill off any adults. It is best to isolate infected corals and repeat the dips as necessary until the flatworms are gone. Red Flatworms are a little easier in that you can treat with Flatworm-Exit directly in your display. Some species of wrasse are known to eat flatworms which makes them a great utilitarian fish to add into your reef. 


TubewormsPhoto Credit: reefkeeping.com

Tubeworms and Feather Dusters

For the most part, these stationary worms don't cause too much trouble. Most would consider them benign or even desirable as they can help to keep the tank clean. They don't sting corals and won't irritate anything so most hobbyists just leave them alone. The problem can result when they are left to grow uncontrollably on surfaces inside your tank.  If they grow in great concentrations, it's probably worthwhile to scrape them off the walls of your sump or from inside your overflow box so as not to clog anything up.  

Some wrasse species will eat feather dusters and various tube worms. Outside of that, physical removal is really the best method of control.  They make their way into your tank as hitchhikers on corals and live rock so prevention is all about being diligent in cleaning and dipping new corals and monitoring what gets introduced via live rock.


Ich, Marine Velvet, Brooklynella, and Uronema

It would be in bad taste to leave this list without talking about the most common fish parasites and diseases. Each of these ailments is quite common among saltwater fish and the only way to prevent these in your aquarium is to follow a strict quarantine protocol.

Following a QT protocol is something that is way easier said than done but any experienced hobbyist knows this learning curve that more often than not results in losing livestock. Failing to quarantine your fish or source fish that have been previously quarantined puts your entire aquarium at risk.  

We have a complete video series in which Ryan teamed up with Elliot of Marine Collectors to deliver an easy-to-follow guide to quarantine and disease prevention. Whether you are building a brand new tank or looking to add fish to your existing aquarium, it's never too late to start quarantine. The 80/20 quarantine process was designed to be accessible meaning it's easy enough for a majority of hobbyists to do while still being effective.