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Getting Rid of Vermetid Snails
INTRODUCTION
Vermetid snails are a family of sessile gastropods that are very frequently found in our saltwater aquariums. They are often mistaken for worms but they are in fact snails that spend their adult life in one location and filter feeds by sending out a mucus web to catch organic debris. In this article we cover why vermetid snails can be problematic for your reef aquarium and several treatments you can use to control them.
THE PROBLEM
Let’s start at the beginning. Why are vermetid snails problematic? They can be a nuisance in the home aquarium for a number of reasons.
First, the mucus webs they broadcast can bother nearby corals. In general, coral do not like to be touched by anything. Physically contacting the webs alone can be a source of aggravation. There is some speculation that the mucus webs are not just a physical irritant but might have pre-digestive enzymes that could actively be killing corals. Everything is fighting for real estate on the reef. It makes sense that vermetid snails would have a mechanism to clear out neighboring organisms.
Secondly, they can be a nuisance to YOU when you are performing regular maintenance in your tank. Vermetid snails grow a thick spiral base that tapers into a tube at the top. It is very common to be scrubbing your tank and bump into these tubes thus puncturing your skin. These punctures can lead to infections.
Third, vermetid snails are one of the most prolific hitchhikers. If they find their habitat agreeable, they can explode in population by broadcast spawning. A small number of snails initially can balloon into the thousands in a relatively short period of time. Once they sexually reproduce, their population becomes much more difficult to control.
Fourth, they can be difficult to eradicate from a system. Vermetid snails are well suited to beat dipping and quarantining procedures and once established in your system, they can persist in overflow boxes or inside plumbing for years.
Now that we have covered some background information on these snails, let’s talk about how to control the problem. I say control because it is near impossible,
A: to prevent their introduction, and
B: to fully eradicate them from a system long-term.
You CAN however get to a point where they are a non-issue. Here are five treatment that will help tremendously in that regard. These are not mutually exclusive and work well in tandem with one another for maximum benefit.
TREATMENT #1: QUARANTINE
If you are of the belief that an ounce of prevention is worth a pound of cure, quarantining new arrivals is a good idea. Quarantine is a very good practice that can minimize a lot of headaches down the road. It is important to have realistic expectations with quarantine though. Quarantine is often thought to be magical cure for everything and in practice it is not.
Many pests, vermetids in particular, are VERY capable organisms. Microscopic larvae and eggs have a way of infiltrating tanks. Still, I will never discourage anyone from setting up a quarantine system. Even preventing a single problem makes the whole effort worthwhile but again, if the expectation is for quarantine to completely eliminate all problems you will likely be disappointed. The eggs and snails themselves all but ignore all efforts to dip them. Eggs by their very nature are resistant to almost everything. The snails themselves can close up for days if necessary to bypass any dipping procedure.
Full exclusion should not be the end goal. There are degrees to effectiveness and quarantine is impactful. Addressing the problem at the early stages is very different to trying to address the problem at late stages. If a rock, coral, or frag is covered with the vermetid snails, it is best manages during quarantine.
TREATMENT #2: REDUCE FEEDING
The next few techniques are meant to limit the feeding opportunities for vermetid snails. If you are broadcast feeding your tank powdered plankton foods or liquid foods, it is adding fuel to the fire. Vermetid snails will turbo charge their reproductive cycle if fed aggressively so the first step is to stop broadcast feeding coral foods into the tank. Your corals will be fine for a long time if you stop feeding them. The benefit of feeding corals is seeking optimum color and growth but so long as there is a vermetid snail outbreak it has to be addressed first.
The second recommendation is to rinse your frozen foods. We make our own blend of frozen food at Tidal Gardens with a mix of mysis shrimp, pacific plankton, and krill. We rinse it all out before we portion out 4 oz feeding containers. Even after that it is still a messy food so when we later thaw it out to feed it to the tanks we give it another rinse. It is amazing how much of the fines still comes off. Reducing the amount of excess food in this way will help starve out filter feeders like vermetid snails.
Third, feed your fish smaller portions that are more likely to be consumed quickly. The fish will clear up the water quickly and even if some of the food gets caught in the mucus webs, lots of fish have no problems picking it off of there, essentially stealing food from the snails.
Those 3 tips address limiting food inputs into your water. If you just do this and nothing else, your vermetid snail population long term will be much less of an issue.
TREATMENT #3 INCREASE FILTRATION
The next step is to out filter feed the filter feeders. We accomplish this by using a number of different mechanical and chemical filters to polish the water and make it a nutrient desert for these snails.
The first filter we recommend is a pleated micron filter of some sort. For tanks smaller than 100 gallons, you can try this Mainland polishing filter. It contains a white pleated filter that does a good job trapping all kinds of particulates. If you use this filter for a few hours per day and then rinse out the filter when you are done, it will do a really good job over time. For larger tanks you can use several of these or invest in a larger filter like a Nu-Clear canister filter.
In that same line of thinking, if you have a sump you can use a filter sock or filter roller to more aggressively capture particulate matter. We have some sumps with filter socks and some sumps without. Needless to say we can tell which ones stay cleaner.
A third water polishing technique you can do is to aggressively wet skim your tank. When you dial up your skimmer to pull out nearly clear liquid, it is like doing a water change but it is stripping out dissolved organics and bacteria. A lot of the skimmate in the collection cup is bacteria. There is literature regarding bacteria as a food source for corals and it might be a similar food source with vermetid snails. If you decide to do this method, make sure to clean out your skimmer neck and head first before cranking it up. If the head and neck is dirty, that will get flushed back into the tank. One would think it would skim out first but in practice that’s not the case. Clean first then wet skim.
A fourth technique is to add calcium carbonate powder to your tank. Calcium carbonate clouds your water temporarily and binds up all kinds of stuff in the water and then settles out. In the process it polishes your water. There is anecdotal evidence that doing this calcium carbonate powder treatment a few times will help clean out your water of the majority of particulates and that limits the food sources further. Additionally, the powder gets caught up in the mucus webs and when the snails consume it, they have a bad reaction.
TREATMENT #4 MANUAL REMOVAL
Now that we have gone over a bunch of ways to starve the snails out, let’s now talk about physically removing the snails you have. You can absolutely get in there with bone cutters and remove them by hand. This requires persistence and generally works better in small tanks. Once you have a proliferation in larger tanks it can get a little out of hand. What I like to do is get a siphon hose and use the tip like an eraser to dislodge them from the tank glass and overflows. Another option is to glue or putty over them. It is not something I would do at scale but for smaller tanks it could work.
If the vermetid snail population is excessive on the rocks, you can consider removing sections of the aquascape and just leaving it out in the sun for a few weeks to kill everything off in mass. We’ve had to reset a few rocks here and there. We let the rocks bake in the sun and after a few weeks we hose them off, scrub them and re-introduce them to the system. It takes a little while for them to re-grow coralline but the vermetid snails are no more. This is a way to deal with the problem in bulk rather than individual snails by hand.
TREATMENT #5 NATURAL PREDATORS
The fifth and final suggestion we can offer is to introduce natural predators of vermetid snails. I only know of one that does the trick and it is an imperfect predator to say the least, that being bumblebee snails. Bumblebee snails are a carnivorous snail that really likes to eat other snails and mollusks. It is hard to see them in the act of eating vermetid snails but I can tell that over time the population of vermetid snails decreases in tanks where we have added a few dozen of them.
Bumblebee snails will eat your other snails so that is something to consider when adding them. They might also eat your clams if you have any. Like I said, they are not perfect, but they have worked out well for us. The nice thing about predators is that they are working constantly to bring down the population of whatever pest they are targeting. The key is to introduce enough of them to get the job done but not so many that they devour your other snails.
While bumblebee snails are the only predator I am confident in discussing, I have heard that copperband butterflyfish can help with the problem. This seemed counterintuitive at first but when we looked closer at tanks that have copper bands vs ones that did not, it does appear that there are fewer vermetid snails. It may be coincidence though.
CONCLUSION
In conclusion, there are several different techniques that you have at your disposal to manage vermetid snails. These treatments work well in conjunction with one another and if you can find a mix that you can perform reliably and sustainably, your issues with vermetid snails will be largely minimized.
