Today I would like to talk about Vermetid snails: that they are, how they get in our tanks, what they can do to the reef tanks and, what is more important, how to remove them from the tanks.
If you have been reading my other articles before you would know that I am a big lover of snails. They can be the best friends for our shrimp and an excellent addition to the clean-up crew. I always advise to have them in any tank.
However, Vermetid snails is completely another story. They are pests, which must be removed immediately from the reef tank. Unfortunately, it is pretty difficult to take care of them completely.
Without ado let me tell you what I know.
Vermetid Snails – What are They?
Vermetid snails belong to a peculiar group of sessile, uncoiled, suspension-feeding, marine gastropods that include more than 160 living species. The marine gastropods of the family Vermetidae are a unique group characterized by an uncoiled shell that is attached permanently to a hard substratum.
Members of this family attach their shells on a hard substrate and may be solitary or live in aggregates sometimes exhibiting a colonial behavior.
Vermetid snails of the family Vermetidae occur intertidally and subtidally in tropical (especially in the tropics) and temperate seas around the world.
Note: I need to point out that, unless you are a marine biologist, there is no way to find out what kind of Vermetid snails people usually get in their reef aquariums. Even experts report that taxonomy and systematics of Vermetidae is currently in a state of disarray and many species remain undescribed because of the difficulty in finding diagnostic characters.
Description of Vermetid Snails
Unlike common snails, Vermetid snails do not have a normal coiling shell, one the contrary, their shells become untwisted in post-larval stages. That is why aquarists often believe that they are tubeworms or confuse them with polychaetes worms (the bristle worms, which are quite desirable creatures for the reef tank).
In addition, once these snails choose the place and settle, they do no move from this place anymore. Vermetid snails firmly attach themselves to rock or any other hard substrates to start building their tube-like shell. These tubes are made of calcium and pretty strong.
Note: Vermetid snails do not grow on the skin or the fleshy part of a coral. They also avoid wood as a substrate to settle on. They need something completely inert.
Depending on the species, the size of the tubes can vary from 1 cm or less (0.4 inches) to 10 cm (4 inches) or even more. The form of the tubes can be also different. Vermetid snails do not build them straight all the time, sometimes they can have a branch-like appearance as well.
The last whorls appear mainly sculptured by a distinct dorsal chord, which becomes more marked on the last
whorls. The color of the entire shell is often creamy-brownish, stripped by darker lines. The surface appears almost smooth, apart from the growing lines.
Another interesting fact about these snails is that they do not live in the tubes. Vermetid snails live right at the base of the construction. Basically, these tubes for them like doors. Some Vermetid snails can even close these doors/tubes with an operculum (like many common snails do).
How Vermetid Snails Feed
All species of the vermetids feed by filtering particles from the water surrounding them. Their diet consists mostly of plankton, fragments, and detritus. To do so Vermetid snails feed by excreting a mucus net that originates from a large pedal gland and spreads into the water via special, grooved tentacles.
The use of mucus nets for suspension-feeding is unique because unlike most passive suspension feeders that have a fixed filtering organ, the mucus net can change size and shape in response to different current conditions and its area can be larger than the animal itself.
Depending on the species of Vermetid snails, the average size of the mucus-net area can range from 3 to 10 cm2. The net remains in the water for 20 to 40 min, close to the substrate, after which it is pulled to the mouth and ingested together with all the trapped particles.
In the studies, biologists observed that Vermetid snails held in containers with still water usually fail to produce mucus nets and that the direction in which the net is extended corresponds to the flow direction. Mucous net feeding is predominately observed in areas of high water flow. Hence, currents appear to affect net spreading.
How Vermetid Snails Spawn
Given this sedentary lifestyle, Vermetid snails have also evolved unique reproductive behavior and juvenile development. This reproductive mode allows for the highly successful invasion and establishment to new areas.
Males produce pelagic spermatophores which are suspended in the seawater and entrapped by the mucus net of the female. So, female Vermetid snails capture the spermatophore in their mucous net, transfer it to the mouth, and via a biting action, eject it packet into the mantle cavity for fertilization.
Females carry egg capsules in the mantle cavity freely or attach them to the inner dorsal shell. Once again, depending on the species female Vermetid snails can have up to several dozen egg capsules. Each capsule can contain from 1 to 40 embryos.
After hatching juvenile Vermetid snails locate suitable substratum and settle on it. In most cases, settlement and attachment occur within 24 hours of hatching if a suitable substratum is available or they may delay attachment for several days in the absence of a suitable settlement surface.
Next, juveniles experience morphological changes of the head and foot, to the adult feeding form. It occurs within 2 – 3 days after attachment to the substrate.
How Vermetid Snails Get in our Tanks.
Actually, it is very easy to accidentally introduce Vermetid snails into your reef tank. In most cases, snails will hitchhike on live rocks and corals and make themselves at home in your tank.
Often they are just too small to see and a few weeks (or even months) later, you start to see strange tubes in the tank that spread some kind of ‘web’.
Sometimes snails can come with new livestock (fish, shrimp, snail, etc.). I mean in the water from a seller. You put the fish or shrimp in the tank and the eggs of these snails come with it. A few weeks later, you have Vermetid snails in your tank.
What Vermetid Snails Can Do to the Reef Tanks
In nature, Vermetid snails are among the most important bioconstructors (reef-builders) in the marine environment. However, in home aquariums, they are not just pesky pests. Vermetid snails can be pretty destructive.
Most aquarists complain that Vermetid snails bother coral and mushrooms due to the feeder webs. They sprout up in between the heads and cause them to stop opening. As a result, corals do not get enough food, become weaker and die, eventually.
Of course, some lucky aquarists say that Vermetid snails did not have a negative effect on their corals. Even more, their SPS grew over them and sealed up the tube, so the snail died from being suffocated.
Well, as I have said earlier, there are more than a hundred different species of Vermetid snails. Some of them can be more harmful than others. In addition, corals also vary in their susceptibility to damage from the mucous net.
Nonetheless, I would not take any risk. That is why it is so important to remove them as soon as you can identify them. In addition, their hard shells are pretty sharp and can easily pierce the skin on the fingers. So, be careful with that.
Interesting fact: Do you know that scientists use Vermetids as a potential bioindicator for global changes, particularly rising sea levels, surface seawater temperatures, and ocean acidification? In addition, some Vermetid species have been listed among the threatened habitats in the Mediterranean Red Data Book of threatened marine vegetation (UNEP/IUCN/GIS Posidonie, 1990).
How to Remove Vermetid Snails From the Tanks
Now I have come to the most important part. Still, no matter what precautions you take you may find the tank infested. So what can we do to remove Vermetid Snails from the reef tanks?
Unfortunately, I need to start off by saying that Vermetid Snails are very resilient at being this nasty nuisance pest. They are not going to leave on their own and can easily ruin the hobby. Lots of aquarists simply gave up, restarted the tank and wiped out everything there.
Nonetheless, there are still ways to fight them. Although it will take a lot of time, nerves and … foul words.
1. Manual Removal
Remove Vermetid snails yourself. You can use coral cutters and magnifying glass for this. Using sharp and dull dental tools can work too. Ideally, you need to take the rock/coral out.
Of course, this is the most tiring and exhausting approach. It will take a while for you but it will be the safest way to deal with snails anyway.
Important: You need to remove the base (knobby part) of the tube. Use a scalpel or razor if you cannot remove the base. Be careful with the sharp tools!
Once Vermetid snail senses the danger, it goes all the way down to the base. The snail itself actually lives in the bottom part of the base. Therefore, if you cut off the top portion, Vermetid snail will just grow a new tube.
Even more, according to the study, many vermetids produce temporary feeding tubes that can be broken and re-molded by the animal. They can also grow around obstacles thus enhancing successful competition for substrate space.
2. Manual Puncture
To do this you will need a very thick sewing needle or an awl. Puncture their tube and base to be sure that you got them. Sometimes it can be a little difficult to find that section but lancing may be just the way to deal with them.
Warning: DO NOT be too overzealous! Lots of dead snails can cause ammonia spike and crash the tank.
3. Glue Method
This method is particularly good if you cannot get out the rock or just do not want to disrupt anything in the tank. Glue their anterior end of the tubes to ensure that the snail is not receiving oxygen food or able to reproduce.
The only problem with this method is that Vermetid snails will start rotting inside their tubes. So, it can cause a tank crash if a lot break at the same time.
4. Introduce Predators
There are multiple reports that Bumble Bee snails eat Vermetid snails. Yes, it is true. However, keep in mind that these snails are not their prime food choice. That is why it is often hit and miss at best anyway. What works for some does not work for many others.
In addition, their effectiveness depends on the location. For example, if Vermetid snails are inside of you rock or in small crevices, Bumble Bee snails will not be able to get there and Vermetid snails will just keep reproducing.
There are rumors that Yellow Coris Wrasse and Emerald crabs can help you out with Vermetid snails. Well, this is not true.
When I was writing my guide about Emerald crabs, I did extensive research and could not find any proof for that. The same goes for Yellow Coris Wrasse only they will eat all your cleaners but Vermetid snails.
5. Feed Less
Vermetid snails are filter feeders so feeding less can starve them out. Of course, we do not want to starve our corals as well. Therefore, be ready to spot feed them.
6. Coral snow
Coral snow clarifies water and removes suspended particles. As a result, Vermetid snails will starve. Combine it with feeding less for better results.
7. Chemical Removal
Personally, I do not recommend it but I need to list it anyway. I have always tried to keep things as natural as possible.
Basically, this is the last straw. If none of the above mentioned methods seem to be working. If you are completely fed up with these snails and want to eradicate them once and for all. Then you can try hydrochloric acid method (read more here).
Warning: It is EXTREMELY CORROSIVE AND DANGEROUS. You must wear eye protection, plastic gloves, and a respirator. Do this outside in a vented area with a slight breeze blowing AGAINST YOUR BACK so the gas does not harm you.
How to Prevent Vermetid Snails
These snails are no joke and can become a nightmare to get rid of. Prevention is better than cure.
Obviously, the best way to keep Vermetid snails out of the tank is to head off the problem before it takes hold. Therefore, always quarantine everything! I seriously mean it.
Quarantine absolutely anything coming from another source that may have been in contact with any biological material. If you see Vermetid snails at the local fish store – DO NOT buy anything there.
Have a very strict coral quarantine – at least 30 days.
If you practice an extended quarantine you will notice that there are Vermetid snails and can deal with them accordingly.
Vermetid snails are a real problem for the reef tank. People often do not realize how invasive they are until they get a colony growing on everything. If you see one there’s going to be more. They multiply like crazy, and unfortunately, they are a challenge to get rid of.
Let’s summarize what we can do to get rid (avoid or reduce) Vermetid snail infestation.
Use extensive quarantine for everything that you are going to put in your reef Preventing is better than cleaning up.
Do not overfeed. Overfeeding is the most common trigger for Vermetid snail infestation. If you stop overfeeding, it will reduce their reproduction rate and it will be easier to control by other means.
Manual removing all these snails is a pain but this is the most effective method.
Introduce Bumble Bee snails to control the snails. Consider them just a secondary backup.
Do not relax. These pests are insidious – you think you have them all, and more Vermetid snails pop up.
If you do all of those things, you will be able to remove snail or reduce them to a point where they will not bother you anymore.
Abundance of the reef-building Petaloconchus varians (Gastropoda: Vermetidae) on intertidal rocky shores at Ilha Grande Bay, southeastern Brazil. Anais da Academia Brasileira de Ciências (2017) 89(2): 907-918, http://dx.doi.org/10.1590/0001-3765201720160433.
A new Vermetidae from the Eastern Atlantic: Vermetus bielerin. sp. (Gastropoda Caenogastropoda). Biodiversity Journal, 2017, 8 (4): 907–914.
A new vermetid from the west coast of Mexico (Gastropoda: Vermetidae). Gardner, S.M. (1989). Venus, 48(4), 250–254.
Cretaceous l-axispira and a discussion on the monophyly of vermetids and turritellids (caenogastropoda, Mollusca). Geologica et Palaeontologica 31: 257–274, 1997.
Three new vermetid gastropod species from Guam. Micronesica 39(2): 117–140, 2007.
Bieler R, Collins TM, Golding R, Rawlings TA . 2019. A novel and enigmatic two-holed shell aperture in a new species of suspension-feeding worm-snail (Vermetidae). PeerJ 7:e6569 http://doi.org/10.7717/peerj.6569.
Reef building Mediterranean vermetid gastropods: disentangling the Dendropoma petraeum species complex. Mediterranean Marine Science. 17/1, 2016, 13-31. DOI: http://dx.doi.org/10.12681/mms.1333.
Mucus-net feeding on organic particles by the vermetid gastropod Dendropoma maximum in and below the surf zone. Marine Ecology Progress Series. 2005. DOI: 10.3354/meps293077.
An overview of the recent vermetids (Gastropoda: Vermetidae) from Brazil. Strombus 19(1-2): 1-8, Jan-Dez. 2012.
Recent introduction of non-indigenous vermetid species (Mollusca, Vermetidae) to the Brazilian coast. Mar Biodiv (2018) 48:1931–1941. DOI 10.1007/s12526-017-0702-7.
The Vermetidae (Mollusca: Gastropoda) of the Hawaiian Islands. Marine Biology t2, 8t–98 (1972).
The Evolution of Vermetid Gastropods. PACIFIC SCIENCE, Vol. IX, January, 1955.
On the identity of “Vermetus” roussaei Vaillant, 1871 (Mollusca, Caenogastropoda, Vermetidae), with the description of a new species. Zoosystema. 2000
The Vermetidae of the Gulf of Kachchh, western coast of India (Mollusca, Gastropoda). ZooKeys. 2016 DOI: 10.3897/zookeys.555.5948