FAQs about Marine Snail Behavior Related Articles: Gastropods, Sea Slugs, Mollusks, Abalone, Related FAQs: Marine Snails 1, Marine Snails 2, Marine Snails 3, Snail ID 2, Snail ID 3, Snail ID 4, Snail ID 5, Snail ID 6, Invertebrate ID, Snail Selection, Snail Compatibility, Snail Systems, Snail Feeding, Snail Disease, Snail Reproduction, Mollusks, Sea Slugs, Abalone,

Snails & Magnesium Levels     11/18/14
Hello,
<Hi there>
I am curious if high magnesium levels are still considered to relax snails to the point of falling off the glass.
<Yes; under many circumstances>
The replies on the topic are from 2006 and 2007. Just making sure there haven't been new developments on the topic. Also, from reading the replies as long as the magnesium is 3x the calcium, then it shouldn't affect the
snails negatively. Is this correct?
<Also so>
Thank you for your time!
Alyssa
<Welcome. Bob Fenner>

Trochus Left His Shell -- 8/21/11 Hi, <Hello Guy, Lynn here this evening.> Early this morning my partner saw one of our Trochus snails half way out of its shell. At that time she said that nothing else was around it, but that the shell was between the heater and the aquarium wall. <Uh-oh.> Soon he completely left his shell and has been since climbing around on the glass near the top of the aquarium. <Yikes. Snails become separated from their shells for a variety of reasons. Typically though, what occurs is that a snail will become wedged/stuck somewhere and in an effort to free itself, will twist its body to the point that it detaches from the shell. At this point, the damage is done as the two cannot reattach.> Please see the attached photo (sorry for the poor quality, it was the best we could manage). <No worries, I can see the problem. Poor little thing.> Perhaps he got stuck there although the shell was removed quite easily or was at some point pestered by another animal -- we just don't know for sure what would have caused him to do this. <It could have been stuck, the heater came on, and the snail did what it could to get away from the heat.> We have placed his shell near where he is on one of the pipes with hopes that he will find it and climb back in, but we don't really have high expectation that this will happen, or even be helpful if he did as we don't know if they can reattach. <Unfortunately, no. In addition, snails that have become separated from their shells don't typically last long because of their increased vulnerability to predation.> Any advice? We of course want to help this poor animal in any way we can, but are having trouble finding any information pertaining to a snail out of shell. <The best thing you can do at this point is to put the snail in a protected area away from any 'pickers' (shrimps, crabs, hermits, nipping fishes and the like) -- perhaps in a refugium or sump.> Thank you, <You're very welcome and best of luck to y'all!> Guy <Take care, Lynn Z>

Re: Trochus Left His Shell -- 8/23/11 Just FYI <Hi Guy> Well, yesterday we moved the poor snail into a little quarantined area adding a strip of algae, but he passed away sometime today while we were at work. <I'm so sorry. I knew his chances weren't good but I was hoping he'd be the exception and survive.> Thanks for the advice, <You're very welcome. I just wish that there had been a better outcome.> Guy <Take care, Lynn Z>

Spitting Stomatellid -- 7/14/10 Hello Everyone, Dayna here. <Hello Dayna, Lynn here this evening.> Fantastic Site. <Thank you kindly.> I have successfully identified 4 new additions to my tank, through this site! I do have a few questions. I have 4 Stomatellids roaming around my tank. <Love'em!> Usually I observe them most active at night. <Typical> Today, however, one boldly climbed up one of my corals, posed itself on its hind, <Nice photo!> ..and spit out a cloud of white particles which I am only guessing is eggs. <Yep, it's funny to see them 'stand up' like that, isn't it! Males release a cloud of sperm in a series of puffs and females release what's usually a rather gelatinous mass of eggs that settles to the substrate and soon dissolves, releasing the embryos. Thankfully, although the young go through a free-swimming larval phase, it's of short duration, so a good many individuals survive to become beneficial little algal grazers.> How many of these little guys are too many? What is the gallon per Stomatellids ratio that would be considered healthy? <Hmmm, honestly I don't think I can give you a quantity per liter/gallon. Instead, I can relay to you that in the absence of predation, their population should be controlled by the amount of food available. What I'd suggest is gathering up some of the extras and giving them away to fellow hobbyists. Perhaps you could even sell or trade some for a frag or two!> Thank you! I love this site! <You're very welcome and thank you!> Dayna Macdonald, Chief Stewardess <Take care, Lynn Z>

What Is My Snail Doing? Sudden Influx of Snails, Possible Reproductive Event - 6/24/10 Hello to all! <Hello Alice, Lynn here today!> I recently had a massive snail explosion, woke up one day and there were hundreds of tiny baby snails all over my 30g tank. <Neat!> I have been picking them off every few days and throwing them away. <Say it isn't so! Why not give them away to local hobbyists, sell, or even them trade for livestock/products at your local fish store?> (I think they are Turbos) My question is what is my snail doing?? It doesn't look like the pictures of snail eggs... is it dying and spewing sand? <I don't think so, no. How is the snail doing today? It could have shed some sort of mucus or released/deposited a gelatinous egg mass while positioned on the glass and then fell over somehow. Whether mucus or gelatinous, the substance would likely have become imbedded with sand grains. It's also possible that the snail simply crawled across a patch (of who-knows-what on the substrate) that once grasped by the foot, separated from the underlying sand and caused a loss of traction. At that point, the snail probably fell over trying to gain purchase and ended up with the patch stuck to its foot in the position seen in the photo. By the way, can you still see any evidence of this clump/mass? As for the 'babies', their sudden appearance does sound like some sort of overnight hatching event, but I'd need to see a photo of one as well as a list of resident snail species in order to confirm and/or determine where they came from. We also need to rule out Collonista snails, also known as 'Mini-Turbos'. They're mostly nocturnal, beneficial herbivorous hitchhikers often mistaken for juvenile Turbos. Depending on the species, they can reach ~1/4' across but most measure 1/8' or less. For more information on these and a photo for comparison, please see the FAQ titled 'Need an ID on a snail: Collonista sp. - 1/5/08' at the following link: http://www.wetwebmedia.com/snailidf14.htm .> Thanks in advance <You're very welcome.> Alice <Take care, Lynn Z>

Lethargic Snails: Possible Lack of Food - 5/13/10
Hey crew,
<Hello there Sam, Lynn here today.>
I have recently noticed that my Turbo snails have become lethargic (One clings to a rock, moving an inch at most a day, while the other has been retracted into its shell, motionless).
<Hmmm, that's not good. You might want to give the retracted, motionless snail the "sniff test" to make sure it's not already dead. Trust me, if it is, one sniff will prove it. If you have tongs or gloves, this would be a good time to use them. The last thing you want on your hands is dead snail juice - yikes! By the way, how long have you had these snails? Do you know what species they are? Are they the only snails you have? If not, how are the others doing?>
My clownfish is still feeding, however spends most of its time swimming into the glass in the bottom corner next to the 15-gallon rated heating fixture.
<As long as the fish is still feeding and you don't see any other outward signs of disease (white spots, etc.) then I wouldn't worry too much. Clowns can exhibit some pretty strange behavior at times but be perfectly healthy. I'd just keep an eye on it.>
My tank is a 14 gallon bio-cube, 78 degrees,
<That's on the low end, but okay.>
..with all parameters acceptable (zero nitrites, nitrates, ammonia, etc.). I have not yet measured important trace elements such as magnesium and phosphorous
<Phosphates? I take it that you're not adding anything (like magnesium) without testing first, right? Too much magnesium can have a negative effect on snails in that it works as a muscle relaxant. The main symptom is usually the inability to hang onto the glass. If you're adding it, definitely stop until you get the test kit. It would also be a good idea to perform a water change.>
..as my order for those test kits is going real slow.
<It happens>
In the meanwhile, do you have any ideas as to what may be afflicting my tank?
<Hmmm, well several things come to mind (if it's not the magnesium issue). First of all, the snails may well be starving. Turbos have huge appetites and two in a 14g is too much unless you really have a runaway algae problem. Honestly, I wouldn't recommend one in a tank that size, much less two. Fortunately, they'll accept dried seaweed sheets (Nori) that you can get either at the grocery store (the same sheets used for sushi), or at a local fish store. I would rubber band some to a rock and place it near the Turbo that's still clinging. I'd also pick up the other (confirmed alive) snail and place it on, or next to, the seaweed covered rock and see what happens. Hopefully they'll both respond and begin feeding. Beyond the possibility of starvation, sometimes Turbos 'home' in on one spot and stay there during the day after spending the night grazing algae off the glass. It can appear that they're inactive when actually they're just 'hanging out' waiting for darkness to fall. What's troublesome though is the combination of an inactive (but thankfully still clinging) snail and one that's just lying there. That's not good.>
I have checked the archives and haven't seen anything about "lethargic snails" and do not expect them to be old, as they are under 2" and seemed to deteriorate at the same time.
<My guess is starvation. Do try the seaweed sheets. If the snails respond, I'd make sure they were well fed then try to exchange both for a single (much smaller) individual or something else entirely (maybe Cerith snails or perhaps Trochus) at your local fish store. Turbos are unparalleled when it comes to cleaning large swaths of algae, but unfortunately, they can exhaust the available food supply in a hurry and starve to death without supplemental feeding.>
Warmest regards,
<Take care>
Sam Sutton
<Lynn Zurik>

Re: Lethargic Snails: Possible Lack of Food - 5/14/10
Thanks for the prompt reply, Lynn.
<My pleasure, Sam.>
I did have quite a few diatoms (and still have some) and a bit of green algae began to take off as well. I have not added any magnesium as of late, so I think starvation may be the culprit.
<Likely so>
Perhaps the long period (2 months) of a diatom diet led to their current situation. I have quite a bit of dried nori
<Great!>
..and will be sure to try placing it near the snails as suggested. Neither are dead,
<Even better!>
..and if I can get them both to start feeding I will probably see if I can get them over to the LPS before they starve.
<Sounds good>
Would Nassarius snails be a better alternative or should I just scrap the "band-aid" solutions altogether?
<Well, Nassarius snails are scavengers so they won't help with any algae issues. Personally, I'd scrap the band-aid solutions and get to the bottom of the diatom and algae issues. There's a ton of info at WWM regarding both.>
Many thanks,
<You're very welcome.>
Sam Sutton
<Take care, Lynn Z>

2/21/2009 Snail that is smoking, menthol or non-menthol, what would the Surgeon General say?? Hello Crew, <Hi Rudy> I need your help. I have a snail in my marine tank, it is small in size, and its face looks yellow, and was throwing smoke, several times(more than 20times), I noticed this after I had just done a water change. Is it mating ritual or harmful? <Mating, not harmful, though do make sure that your change water has the same parameters (pH, Alk, etc.) as the water in your tank. Some invertebrates will release eggs and\or sperm if they are stressed> Thanks Rudy <Mike> <<Thanks Mike. <My pleasure Rudy> I had video it as well, if you would like I can email that too, but it was filmed with my blackberry. <That's ok, it is a very common thing with snails.> Btw, when I read menthol, I just freaked out! Thanks for the one year eliminating scare from my life score board :-) <Hee... sorry, I couldn't resist, I just had this picture of a snail standing on the street corner smoking a cigarette.> Thanks for your fast reply. <No Problem> All the best, <and to you> Rudy <Mike> >>

Sneezing snail 11/02/08 I've been having trouble keeping turbo and Trochus snails in my tank, yet my two fish, crabs and other snails are thriving. My water parameters seem fine (1.024 salinity, .15 ppm nitrates, 8.2ph, 0 copper, stable temp). My LFS verified these tests. I was watching my last turbo very closely tonight and I caught it "sneezing". It would draw up on its foot and come down very quickly. It did this a number of times. Could it be trying to expel an irritant or parasite? Around the same time, I caught an amphipod racing up and down the snail. I didn't think regular amphipods bothered snails, do they? <The snail might be either spawning or simply feeling out for somewhere to crawl. The amphipods aren't likely bothering the snails.> Thanks! <De nada, Sara M.>

Question about ozone and snails, beh./repro. induced 10/15/08 Hello there guys and gals, Grant here. <Howdy> I have what I believe are margarita snails in my 210g tank. They are about an inch across, pretty squat (basically as wide as they are tall) and the fleshy part at the base has 8 or 10 little flanges that stick out around the meat. So for instance, if they are on the front glass and I can see their foot, the little flanges almost make a star pattern sticking out sideways from the foot. I hope that is a good enough description for you to go off of. They eat algae also. <Ok> My question is this... I hooked up a Red Sea ozonizer to my tank last night. Never before have I seen my snails spawn in my tank, but last night they did. The males were almost constantly putting out a small stream of milky liquid for around a half hour and the females would jerk and compress every couple minutes and squirt out a batch of eggs. I find it very coincidental that the same night I started using ozone is the same night the snails spawned, which I know in some crustaceans is like a last ditch effort to ensure the survival of the species. I think its Tridacna clams that can be manually enticed to spawn by adding slight amounts of acid or alcohol to the water? <Yes> If there such a thing for snails? <Yes> Too bad I just hooked up ozone, because those little eggs have no chance of surviving through that. <Mmm, all sorts of life is generally reproducing in captive systems pretty much continuously... not a worry> Anyway, I'm only injecting 50 mg/hour of ozone into the tank until the ORP probe starts reading accurately which I hear can take up to a week. I figure 50 mg in a 210 tank is definitely not pushing my limits. <Correct> It's being injected via the John Guest fitting on my Aqua-C EV-240 protein skimmer. Quick side question, I've never used a John Guest fitting before... is it really as simple as just taking the air hose and jamming it into the hole? <About this, yes> I actually unscrewed the threaded fitting from the skimmer and thought I had to do something to get it to accept the air hose, but as far as I can tell you just push the air hose in firmly and it grabs it plus makes a seal. <Yes, yep, uh huh~!> Thanks for all you guys do! Grant <Welcome our friend. Bob Fenner>

Snails won't move! 8/3/08 Hi guys! Have read the pages on snails, but none seem to quite solve my problem... I had a bit of an ammonia/nitrite spike in the tank which killed a few things off... but have now got the tank back to normal so am trying to restock things I lost (having learnt a lot from the experience!). Anyway, I bought some snails from the LFS which were crawling around happily there but after being introduced to my tank refuse to move (or move only a tiny amount). Sometimes they extend their foot and push themselves over on their sides (I know there's the problem with some species doing this but my snails are not moving around and then falling over accidentally, they don't move at all!). It's almost like they've lost all co-ordination. This is fairly unusual though, most of the time they don't move at all... I thought it might be the snails themselves so swapped for some other snails - which I made sure were active in the shop's tanks - and they did the same once they were in my tank! <Yes... "is" the tank... water quality> The snails were acclimatised slowly over several hours (around 3hrs in one instance, 5 in the other). They've now been in my tank 24hrs and no change... Tank tests show: Ammonia, nitrite, nitrate, phosphate all zero. Salinity 34-35ppt pH 8.2 Temperature 25 (stable with combined heater/chiller unit) Alkalinity 3.2meq Calcium 420 Magnesium 1245 I know the magnesium level is slightly low, and from other posts I see snails are quite sensitive - could this be the problem? <Mmm, not too low... right about right... not a problem> Flow is approx 30* tank volume/hour, and fish/corals/shrimps seem happy. Hermit crabs are a bit sluggish but seem ok. I change 5-10% water each week. I'm slightly at a loss! Any suggestions/other things I should test for? Thanks! Richard <Well... the list is rather long (for tests/testing) and incomplete in terms of the sorts of phenomena, elements, compounds that hobbyists can do... Allow me to cut to the chase here and suggest what I would do... massive water changes... I suspect you have a "salt imbalance" problem likely... from supplement (mis) use... Do please write back re what your habits have been here, or just go ahead with some 50% change outs to get back to "just seawater" strength/concentration for the major components... This should solve the snail problem. Bob Fenner>

Re: Snails won't move! 8/5/08 Hi Bob - thanks for this. Checkered history as follows... Tank was set up beginning 2007. Because everything was going well, and I had no problem with nitrates my first mistake was to do no water changes at all. <Mmmm, yes> My second mistake came at the end of 2007 when I introduced a sand-sifting starfish. This stirred up all manner of toxic waste accumulated in the sand over the twelve months and resulted in several deaths... Having learnt these lessons, I took the starfish back to the LFS and commenced water changes. I did 10-15% every other day for around two weeks, then 10-15% once a week for several months, then 5-10% every week for the last month or so. The only real supplement I've used is Seachem Reef Plus (in addition to Seachem buffers, calcium and Red Sea Iodine). <Mmmm> Your chemical imbalance idea sounds a good one though - and something clearly I can't test for. Given the above info do you think it would still exist? <Yes... much of the chloride in particular here...> My other thought on this theme is that when I started water changes I was using Red Sea salt for RO water. <With RO water I take it> When I'd used a couple of buckets worth of that, I switched to Seachem Reef Salt. The two presumably have slightly different compositions - could switching salts have exacerbated the problem?? Thanks again! Richard <The SeaChem product is superior... not likely a problem with this switch. Again, I would execute one, two largish water changes (50% let's say) a week or two apart... and try some snails again. Bob Fenner>

Astraea Turbo Snails, beh./hlth. -02/24/08 Crew, Thank you in advance for your response. I've done several searches for this but can't find anything. 5 of the 15 Astraea turbo snails that I recently added to my tank are at the top waterline on the glass and have been for 48 hours now. All other occupants seem fine. I read somewhere that snails need to "breath" and that this is normal. <Um, no, not air.> That sounded fishy to me (no pun intended). All water parameters check out fine. Thanks! <It's not unusual for snails to like this part of the aquarium. There's a lot of "stuff" that grows up there that they like to munch on. But just in case, you might want to take a look here: http://www.wetwebmedia.com/snaildisfaqs.htm> <Best,
Sara M.>

The snail who left his shell 3/29/07 Howdy, <Hey there> Here's a weird one for you. Today I noticed one of the Jumbo Nassarius Snails in my 180g Reef seems to have left his shell. No signs of trauma. He is still alive and moving around somewhat strangely, but not sickly or injured. I even found his shell, and it's in perfect shape. Water parameters are all fantastic, no known snail predators present. There are two Tunze stream pumps that I wonder if they could have shucked him. <Mmm, not w/o grinding up the soft body> Otherwise, I don't know. Have you ever heard of this happening before? <Mmmm, yes... from overt dire water chemistry (big, fast shifts in alkalinity mostly), and parasites of the snail invading their shells...> and if so, what was the cause? Everything else, corals, fish and inverts look great and are doing well.. <Perhaps this last> Thanks, love your site. Check out the picture, I hope I shrunk it down small enough to avoid crashing your server. Mike <Yes, thank you... Perhaps this "slug" will regenerate a new shell... Bob Fenner>

Thanks, and a Story re Stomatella Snails (beh.) 1/29/07 Dear Bob, et. al.: <Greetings John, Mich with you this evening.> First of all, many thanks to all of you for your fine WWM resources. You have all helped me gain a tremendous amount of valuable insight into the reef aquarium hobby, at times calming my fears, at others helping me form new strategies, and most always helping me to stay out of (too much) trouble. <Hehe, this is good.> It is a constant learning experience, and the challenge is greatly alleviated by useful knowledge and sense. <Glad to hear!> I have a 75g reef tank with about 100 lbs. of live rock and a 3" sand bed. This tank had been set up for at least a couple of years by the prior owners, but had been sadly neglected -- inadequate lighting, insufficient water changes and regular maintenance, etc., and the live rock and sand were really not very "live" at all. The sand was absolutely full of detritus. After moving the entire works, setting things back up, adding a new skimmer (AquaC Remora Pro), 300w of 10k and 70w of 20k MH lighting, some new additional live rock and sand and 4 months of babying, this microcosm is now doing extremely well, and has some very good diversity of life... not all to my own credit, because you and your advice also deserve some of the credit. Some "Live Sand Activator" from Coral Dynamics really kick started the sand bed, and a couple of other live micro-critter inoculations have the now very active sand bed well on its way to a stable equilibrium. The tank never did cycle (measurably, at least), and has never registered any reading for ammonia, nitrites, nitrates, or phosphates. <Awesome!> The tank now houses the 2 yellowtail damsels which came with the original setup, a black velvet neon damsel (which was rescued from another marine tank after being attacked nearly to death by other damsels, and who has doubled in size in 3 months), a lawnmower blenny, and a powder blue tang (which I had great trepidation about adding, but who is healthy, growing, and truly thriving). I've gradually been adding corals over the past couple of months - a couple of Acropora frags, two Montipora, a Pocillopora, a pumping Xenia, and most recently a yellow Fiji leather. All are thriving (though the Xenia is rather finicky), have plenty of space, and I am done adding anything for the foreseeable future. WWM and Bob's and Anthony's books have really helped me tremendously. <The website and the books are an invaluable asset to this hobby. I too would have been at a total loss without them.> I don't have a question today, but do have a comment / story to share. <Very good.> After adding something six or so weeks ago, I began noticing tiny slug-like creatures which grew quickly to about 1/4" to 3/8" length. Within a couple of weeks there were hundreds of these animals in the tank, most notably after dark. They were hard to see on the rock since they were well-camouflaged, but they moved around very quickly, much more so than the Cerith, Astrea, and turbo snails. After seeing one of the larger of these spewing milky stuff one morning (obvious to me that this was a reproductive event), I earnestly needed to find out what these things were, fearing a pending plague. After much searching, I finally determined that they were Stomatella, and that I did not indeed have a problem after all. Their population has by now become self-regulating, and there is always a full range of sizes of these snails in the tank. <Most excellent! These are a great addition to any saltwater tank.> Yesterday I took out two MaxiJet 1200 powerheads with Hydor Flo rotating heads (an absolutely wonderful product for the money, IMO) to (experimentally, at least for now) replace them with Hydor Koralia powerheads. (So far I'm very impressed with these, and the general water movement in the tank is much improved, though time will tell the tale). Upon removing the Maxijets, I picked off several Stomatella, putting them back into the tank. After about 30 minutes (with the Maxijets sitting in the kitchen sink, rinsed in tap water), I got around to their complete disassembly and cleaning. I found several more of the Stomatella inside the powerheads, and was very surprised to find them still alive. <Yes, pretty hardy creatures.> Assuming that following what they had just been through they were almost certainly doomed, I took three of them back to the tank and dropped them into the water anyway. <Always good to be an optimist.> Fluid dynamics being as it is, all three floated to the bottom and landed on their backs. They squirmed around for a few seconds trying to right themselves (they are really adept at that when they land on rock), but none were able. Then all three squirreled their heads around and began picking up grains of sand, placing them on their "bellies" (feet), and moved the grains along to the back end of their feet. After doing this with 4-5 grains of sand, they had gained enough weight (apparently) to squirm one more time and roll over, after which they took off on their merry ways. I was pretty amazed -- what a remarkable behavior this was! Is this a great hobby or what??!! <What a world!!! Amazing isn't it?!?> Sorry for the length of this message, and again, thanks so much for all your insight and assistance. <No apologies please! Thank you for the kind words and sharing your delightful story! -Mich> Kind Regards, John

Turbo Snail Issues 6/3/06 I had 3 zebra turbo snails. After a couple weeks I now have 1. It went to the back of the tank where I have some algae planted and released black pellet looking things. <Waste pellets, snail poop.> I don't know if its relieving its self or what but its all around it in the sand and on its shell. Hopefully you know what this is. Thank you for your time. Love the site. <Chris>

Trouble ID'ing snail and what is it doing exactly? 3/4/06 One of the members of my site has this snail. I think it may be a type of Mitra species. <Does look like...> I'm trying to get a positive ID. <Okay... Mitra mitra... common, and big in HI> Also, what exactly is it doing? <Eating or regurgitating a Polychaete worm... the bristles knocked off... looks like more of the latter> I've seen this snail in a normal appearance with a normal foot, but what is this behavior below. Once again, thanks for a great site to help us fellow enthusiasts. I've attached the 4 pictures, seen pasted below, to be sure you receive them. Steve <Thanks. Bob Fenner>

Gas-passing Snail..? More Likely Breeding Behavior Induced by Move 11/12/05 I just, and I mean just, like 1 hour ago upgraded my 60g to a 165g. <<Tres bon bon.>> (It has been set up for a week, with it half way filled with water, some live rock and live sand, and I was doing 5g water switch outs a couple times a day to get both tanks to be the same.) I have one turbo <<Turbo?>> snail, and it was one of the first to go into the tank today. After all the fish transferring was done, I sat down to observe how everyone was getting along. <<Famously I hope. New digs, and I got to hire movers! Yay.>> I see the snail on top of the organ pipe coral. (It's on a bare spot, not on any coral-it died off a little due to ammonia levels, and has been growing back beautifully.) It is standing on its tail, its head up high, not touching anything, and there is more of its body out of the shell than I've ever seen. <<You mean.. your snail was flashing you???>> Its antennae are waving more than usual, and near its eyes, there is kind of a lump or pipe or tube (made of its body). The snail starts to lean over, like its shell is pulling it down, but then it straightens up quickly, and a cloud of...something comes out of the tube. <<Oh my God! Talk about a "money shot"! Ahem.>> It keeps doing this. I pushed it back over so it was in its normal position, but the clouds keep coming out, every minute or so. <<Oh my.. no, I can't, never mind. This is funny.>> I have been sucking the clouds out, as much as I can, with the turkey baster I use to suck or blow things in the tank (does anyone else use one for this purpose?). <<Yes, turkey basters are great! So are large animal syringes (if you can get them).>> Have you ever heard of a snail doing this? <<Yes. And urchins and fish and birds and bees, if you get my meaning.>> Is the stuff bad for the tank? <<Highly doubtful. What I think you've witnessed is some sort of snail ejaculate. Breeding behavior. This is often induced in lots of animals by (you get three guesses here, and the first two don't count).. LARGE WATER CHANGES! Ready for a cigarette yet?>> I've never heard of a snail poisoning a tank, like sea slugs, cucumbers and other creatures can, but I don't know, so that's why I'm asking the experts. <<To quote the Bobster, "Ex-spurts!" No, seriously, snails can "poison" tanks by dying and the following decomposition will, of course, present some pollution, but it is not by any sort of poison or exuded.. umm.. excreta? You're thinking boxfish, sea slug-type poisoning, and I know of no snails that can do that (that hobbyists keep).>> Thanks!! <<I should let you know that your snails have a choice, though they should use protection. Tell them that no, their palms won't grow hair, and they won't go blind if they keep doing this, but it's the best way to avoid unwanted pregnancies. Finally, it's ok, but it should be done privately