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FAQs about Giant Clam Disease: Diagnosis

FAQs on Giant Clam Disease: Tridacnid Disease 1, Tridacnid Disease 2, Tridacnid Disease 3, Tridacnid Health 4, Tridacnid Health 5, Tridacnid Disease 6, Tridacnid Disease 7, Tridacnid Disease 8, & Pest Snails (Pyramidellids...),
FAQs on Giant Clam Disease by Category: Environmental, Nutritional, Social, Trauma, Pathogenic, Treatments

Related Articles: Tridacnid Health: Pinched Mantle Syndrome in Giant Clams by Dr. David Basti, Deborah Bouchard & Barry Neigut, Got Tridacna? A beginner's guide to keeping Tridacnid clams by Laurie Smith, Example Chapter from NMA Reef Invertebrates book, on Giant Clams, Tridacnids, A Brief Guide to the Selection and Placement of Tridacnid Clams by Barry Neigut, Bivalves, Mollusks, Lighting Marine Invertebrates

Related FAQs: Tridacnid Identification, Tridacnid Behavior, Tridacnid Selection, Tridacnid Compatibility, Tridacnid Systems, Tridacnid Lighting, Tridacnid Placement, Tridacnid Feeding, Tridacnid Reproduction, Tridacnids 1, Tridacnids 2, Tridacnids 3, Tridacnids 4, Tridacnid Clam BusinessBivalves, Bivalves 2, Lighting Marine Invertebrates,


Sick Derasa Clam  2/18/07 Hello WWM crew!! <Darrell> I cannot express to you how much your site has helped me out in the last couple of months with researching this very addictive hobby. <Ahh, always a pleasure to read, realize> I spend about 3 hours a night researching and getting ideas from the over abundance of information here. Thank you all so much for all of the work you do and the knowledge/experience you share with us. A million thanks. Now for my problem'¦ <Welcome> I have a 29 gal reef tank with a Millennium 2000 filter, a HOT Magnum Canister filter which contains Nitrate sponge (you'll understand why in a minute) and an Aquarium Systems SeaClone 100 Protein Skimmer (which is impossible to keep adjusted correctly). <Yikes... it's not just you...> The tank has been set up since April 2006 and has done exceptionally well in that time. It contains around 45-50 lbs of live rock and 40 lbs of live sand (approx. 1-1.5' sand bed). My lighting consists of (2) 65W PCs and a 125W HQI, the PCs run for 10 hrs a day and the HQI is on for 8 hrs per day. <With no vacillating heat problem?> I have never had an algae problem so I am wondering if I should increase the photo period for the clams/corals. <Mmm, maybe... what do they look like?> My chemical parameters are pretty consistent and as of yesterday are as follows; PH -- 8.2 Ammonia - 0 Nitrites - 0 Nitrates - 30-40 (I'm fixing that problem now with a refugium and more frequent water changes) <Good approach> Phosphates - 0 Calcium - 470 <A bit high... I'd allow this to drift to 350-400 ppm.> KH - 9.9 Magnesium - 1320 Alk - 3.54 I am currently cycling my 75 gal tank which I have just converted from FW and I just finished the sump and refugium construction which your site was an invaluable tool for understanding and designing and it seems to be working perfectly. <Ah, good> I am planning on using a DSB in the refugium with some macroalgae to help with Nitrates and bugs. I have around 70 lbs of dead rock to which I will be adding another 20 lbs of live rock this week. I plan on also having around 1 inch of live sand in the tank (unless you would suggest otherwise). <Mmm, no... this is about right> This, I hope, will alleviate the Nitrate problem I am experiencing in my 29 gal. <Very likely so> OK, now that that's out of the way, my main concern. I have a Crocea and a Derasa and my Crocea has been in the tank for about 6 months and is doing wonderfully. My Derasa on the other hand is not looking very good at all. It was added about 2 months ago and approximately 2 weeks after adding it the mantle started to appear to be 'scratched'. <I see this> I thought maybe my hermits were walking over it or something so I moved it to a protected area of the tank and it doesn't seem to be improving. <Takes time...> It will react to shadows and will open partially but will no longer open fully and the mantle never extends past the shell. I will include a pic of the 'scratched mantle' for you to see. I have searched all over the internet and your site and the only thing that comes close is the pinched mantle disease but this doesn't seem to be the case here <No> although I could definitely be wrong. I am very naive when it comes to marine diseases. The other tank occupants are a 4 stripe Damsel, Yellow Tail Damsel, Coral Beauty, Clown (Percula I believe), (2) Sally Light Foots, (3) Porcelain Crabs, Emerald Crab, 6 or so Hermits, Snails and several species of corals. <Mmm...> I have examined it many times for Pyramid Snails and have never seen even 1. <Look at the base... the byssus... if/when moving to the new, larger system> If you have any other suggestions, <... Do you feed your sessile invertebrates? Amend same with supplementation? I would> they would be eagerly accepted. I am sorry if this is long winded but I wanted to give you as much info as possible. Thank you again for everything you guys do for the Aquatic community, it is greatly appreciated and highly valued. Darrell West Chester, PA <Please do read the area over re Tridacnid nutrition: http://www.wetwebmedia.com/marind5_5.htm scroll down...> P.S. Thank You Mr. Fenner for The Conscientious Marine Aquarist, I purchased it a month or so ago and I just wanted to tell you, you did a great job. <Thank you my friend. Bob Fenner>

Crocea Death...Searching for Clues - 08/08/06 Hi Crew, <<Hello Jason!>> I just lost the first T. crocea clam I tried to keep in my system, and maybe you can help me diagnose the cause. <<Mmm, unfortunate...let's see if I can be of help...>> It had been in the display tank for about a month and a half, and until Saturday it was looking good (as in, I hadn't noticed any signs of trouble, though they may have been there). <<Indeed, but often with these clams it is too late by the time it is noticed that something is amiss.  And once they start to "go" they go quickly>> Saturday I noticed the mantle was not extending, and worse, the clam was not closing when my hogfish swam nearby, as it usually would. <<Mmm...a very bad sign...generally signals the end is near>> In fact, the hogfish poked its head into the clam! <<Yes...when opportunity knocks...>> Saturday night I did a 5-gallon water change (~65 gal tank including sump) and tested the water.  Undetected ammonia and nitrite, 10ppm nitrate, 0.03mg/L phosphate, 380 mg/L calcium, 8.1 pH, 1.022 salinity, 5.8dKH alk.  Alk was clearly low, so I raised it a bit with baking soda to 6.2 dKH. <<Still a bit low, should be more than 7 dKH>> This morning, clam was closed. I left for the day, came back around midnight, and the clam was being eaten by a hermit crab. Most of its flesh was gone. <<Doesn't take long when scavengers are present...the flesh seems to be "relished" by all>> I inspected the shell for parasites and found none.  I also never saw worms bothering the clam, nor any inside the shell after I removed it. <<Their presence at this point would not have proven anything>> So, whodunit? <<Hmmm...likely environmental mate>> I am not inclined to believe it was lack of lighting, though tell me if I'm wrong.  I have 400W 20kK MH for my 58 gal display, and the clam was in direct light. <<As long as the clam was acclimated to the lighting and was not stressed/weakened by photo-shock then yes, probably not your lighting>> It did often seem pestered by my hogfish, however, and would frequently close up when the hogfish swam by. <<A stressor (the hogfish may even have been nipping at the clam), and likely a piece to the puzzle>> Thanks for any ideas and suggestions to avert future clam deaths! Jason <<Well Jason, there's no way to say with any certainty what caused the demise of your clam.  As stated previously, it was probably environmental...a combination of factors that may include excessive nitrates (clams do appreciate some measure of nitrate, but I would recommend this be kept below 5ppm), collection/shipping stress compounded by the attentions/pestering from the hogfish, out-of-balance earth elements (alk), even a lower than NSW salinity (should be 1.025/.026).  Any of the elements/conditions on their own may not have been a problem, but when combined.......  And something else to consider.  You don't mention other corals in the system, but the presence of noxious organisms such as mushroom/soft/leather corals (Corallimorphs, Alcyoniids) can make keeping clams very difficult.  Increased water changes and chemical filtration (carbon/Poly-Filter) can help, but even then it sometimes is not enough.  Another consideration is that "dosing" in the vicinity of the clam may have poisoned it (especially iodine)...very efficient filter feeders.  All speculation on my part my friend...but some food for thought.  Regards, Eric Russell
Re: Crocea Death...Searching for Clues - 08/08/06
Thanks for the detailed reply! <<Quite welcome>> In fact, I do have a number of soft corals and mushrooms in my tank.  There is large cabbage leather (Sinularia dura I believe), a smaller Sinularia sp., three smallish mushrooms, a few stalks of xenia, green star polyps, and some Zoanthids. <<Mmm...but for the Xeniids, all are quite noxious (Sinularia is some of the worst)>> I did not realize these were incompatible with clams.  Is that a general rule of thumb, or are there certain clams that are better suited to being kept with soft corals? <<More of a "broad" statement...  Clams and soft corals can be kept together with provisions (low stocking density first and foremost), but in a soft coral dominated system you may find "long term" success difficult.  I'm not saying you can't be successful, but you will need to understand the challenge...and you "might" find T. derasa to be a bit more tolerant/hardy in this respect than the other species>> I also use Poly-filters and don't dose anything but a Kalk drip (in the sump). <<Do keep your calcium/alkalinity in balance...important to the clam>> I had let water changes slide for 3 weeks, which certainly did not help. <<Indeed...water changes are your single best tool for success here>> Thanks, Jason <<Always welcome, EricR>>>

Clam question Hello there- My father says WetWebMedia has given him lots of great advice- I have a question about Tridacnid clams (purple/blue (not maxima)......I've had a couple for about a year or so, and they both died the other day, both within about 24 hours.  All I could see was what looked like clear snot, and what looked like pieces of sand in the mucus, .....the clams closed up, and they seemed to have a hole in the bottom of them......the only thing that seemed to be near the clams, were brown tiger tail cucumbers. Have you seen this before? Thanks for your help..... DaveB <Hello Dave, Have you fed your clams weekly?  Marine Snow is a good product to use.<<Uhh, not in all's opinion here. This product is a placebo IMO... has VERY little nutritional value>>  It's not necessary to feed daily, a once a week feeding should be enough. <<Barry Neigut suggests a minimum of 3 times per week... and NOT Marine Snow>> Also, do you change your bulbs on a yearly basis?  Clams do require strong light of the proper spectrum.  Just cause the light lights doesn't mean the full spectrum is still there.  Most clams will only do well under metal halide lighting. James (Salty Dog)> 

Clam Question 1/5/05 <Dave, I have backed up to your original question> I have a question about Trinidad clams (purple/blue (not maxima)......I've had a couple for about a year or so, and they both died the other day, both within about 24 hours.  All I could see was what looked like clear snot, and what looked like pieces of sand in the mucus, .....the clams closed up, and they seemed to have a hole in the bottom of them......the only thing that seemed to be near the clams, were brown tiger tail cucumbers. Have you seen this before?  Thanks for your help..... DaveB <Anytime more than one similar animal dies at one time, it is suspicious for either poisoning, disease or predator.  Your clams were probably T. crocea.  They normally have a large hole a the base called the byssal opening.  It's symmetrical, tear-drop shaped with slightly irregular edges and looks natural and like it should be there.  If the hole you are talking about is small (BB size) and looks as though it was drilled, you have a boring predatory worm or snail.  There are also predatory worms that engulf clams and snails in a blob of mucous to suffocate them and then eats them.  All of these are extraordinarily rare to encounter, but it is possible and would fit with what you described.  Have you recently added any animals that such a critter could have hitchhiked in on?  Catching these beasts can be tricky... baiting them with snails and then watching at night to try and catch them is often necessary.   Best Regards.  AdamC.>
Re: clam question
Hi, thanks for getting back to me....yes, they are Trinidad Croceas....exactly.   <Hee hee! No Tridacnids in the Lower Antilles! Oh, AdamC is out visiting the west coast so am responding in his stead> What happened was exactly what you were talking about, a mucus that looked like they covered the clam, and suffocated them............ but at the same time, it looked like the base was worn away, not by a hole though really.   I added an abalone and a tiger cowry, but other than that all has been the same. I lost one of these about 6 months ago the same way.  I had 3 T. crocea, now just one Derasa left. Thanks, Dave <Please do read through our scant archives on giant clam health: http://www.wetwebmedia.com/tridacdisfaqs.htm and the Related FAQs (linked, in blue, at top) if you haven't already... and on to the references listed. Bob Fenner>


Crocea clam not opening - 12/6/04 Hi Crew!, Hoping someone may be able to help with one of my Croceas. <Sure hope I can help. Sorry for the delay, I was out of town and I thought I had to answer but it got away from me. I do apologize> I have two, both purchased at the same time 6 months or so ago. Both are a little larger than a clenched fist. They sit on very large clam shells (from the beach) <I don't recommend using beach collection in a personal reef collection but if you bleached it then.....> on the bottom of a 75g (corners) with 2 x175 MH and 2 x 96 pc. One has not been extending his mantle and stays almost closed most of the day. <Hmmmm> Some times it is extended a little but not to the extent that the other is. <weird> Params are: ph 8.2, alk 3-4 meq/l, Ca 400. temp 80. Even though not fully extended it still reacts to light change (shadow) I do not know what to do for him. <I would leave him be. Be sure to watch for any pests that may be picking at the mantle. Don't always trust the tang. Also, be sure to try some of the commercial foods directed at clams, such as Reed Mariculture live Phytofeast or their coral and clam diet. Photosynthesis  alone, does not meet all nutritional needs of these animals > My tang does bother him at times but does the same to the other clam and that one could care less <Don't be so sure> Any ideas? <See the above> Thanks. <Hope I am not too late. Sorry for the delay. ~Paul>

Derasa Clam in trouble 12/4/03 I think there may be a problem with my 4 " derasa. Last week, I found what I have now identified (I think) as either part of or the complete byssal gland lying next to the clam... This clam has been in my care for the last year or so and has never exhibited any sign of a problem. It lies on the substrate and isn't attached to anything. Now the clam is showing signs of stress... Poor mantle expansion, slow to react, gaping. Anybody have any idea what the problem might be? <could be predation (look for tiny Pyram snails like grains of rice) or bristleworms at night (inspect after the lights go out)... possibly a crab although more damage would have been/be likely. Then there is the issue of water quality: light shock from a recent and overdue change in lamps or a large water change/change of carbon that increased water clarity suddenly... clams are also sudden to a large influx of freshwater for evap top-off... or spikes of supplements to the tank that are not adequately diluted> I've heard of larger clams expulsing their byssal gland but never 4 " ones and especially not T. derasa... Thanx Simon <this last assumption is not correct, my friend... there is little discrimination by age/species for the expulsion of byssal matter... rather just a matter of necessity by individual when called for. Still... its not an unhealthy maneuver and signs of stress here indicate a larger problem perhaps. Anthony>
Derasa in trouble II 12/6/03
Anthony, Thanks for taking the time to answer. Unfortunately, the clam died ~24hrs after my e-mail. I  was not a happy camper. <sorry to hear it> The water parameters are all fine and out of all the inhabitants of my 110 gal reef, the clam is the only casualty. <different tolerances too to stressors, and "somebody has to be first" as they say. Point being... don't dismiss the potential for a problem just because everything else currently looks fine. Without knowing your full water chemistry, I cannot concur with the evaluation of water quality> (there's also a 6 inch maxima in there) No Pyramidellid snails or bristle worms either. There IS an elusive crab in there somewhere. <yikes... indeed, no crab is truly reef safe> He's grown quite big since my first sighting.(~1.5 inches of carapace) I know he's in there but I don't see him often. <do bait and trap him. Should be easy enough (crabs are greedy). We have tips for doing this in the WWM archives and in our Reef Invertebrates book> Looks like a type of crab I've heard called "shame face crabs" but I can't be sure. Maybe I should be trying to catch him...? Thanx again. Simon <if it is indeed large clawed like a shame-faced crab, you can be assured it is a threat. Those claws are generally built for eating snails and bivalves/clams. Kindly, Anthony>

Clams In A Jam? Afternoon all!! <Hiya! Scott F. at your service!> I have an issue with my two clams as of the past few days they are only ? open. I have had both for years and all other corals and fish are thriving. Is this common in clams. My calcium reactor is working throughout the day and all parameters seem fine. Of late the clams have been emitting some kind of mucus which I assumed was from the newly added calcium reactor. Any advise on why BOTH they have shut for the past two days?? Thanks Stu <Well, Stu- it's hard to say exactly what your clams are reacting to, but it might be possible that some sort of water parameters are out of whack. Usual suspects include ammonia, nitrite, excessive phosphate levels, or rapidly fluctuating pH, not to mention the possibility of "chemical warfare" from stinging cnidarians that may be in close proximity to the clams. Did you recently change lighting? Are you using any new additives, "medications", or foods in the tank that could be a problem? Test the water again, just to be sure. In the absence of these as problems, the other possibility is that someone in the tank has started picking at the clams. Do check the behaviors of any of the "usual suspects" (i.e.; angels, certain wrasses, etc.) to see if this occurring. My advice when these kinds of seemingly unexplained anomalous behaviors occur is to use the old standby of a water change, coupled with use of aggressive protein skimming and activated carbon. Hopefully, with a bit of minor intervention, and the passage of time- things should work out fine, and they'll be "happy as a clam" in no time! Good luck! Regards, Scott F>

Gaping Crocea - 10/07/03 I have a 5" crocea which is gaping, the mantle is recessed, the inlet siphon is stretched as well as other spots on the mantle which looks like skin being stretched and ripped, the outlet hole that used to stick out like a nipple no longer does, just a hole, and when you look in the inlet siphon you can see the sand on the bottom of the tank (it's no longer enclosed. water parameters are ok, any tell tale sign? <Well, the sign to me is this clam will not, in all likelihood, make it another 24 hours. Don't move it though. Leave it be for the now. There isn't much known in the way of clam mortality per se. They seem to waste away quite quickly and for no reason. There are a great many theories, though. Read through our site on clams: http://www.wetwebmedia.com/tridacnidart.htm go through the links. Also, we have a friend of the site Barry Neigut of ClamsDirect.com, who not only has a forum on his site for troubleshooting clams, but he sells, and even consoles problems with clams via email. Give him a try as I am sure he deals with more clam problems in one day than we hear about in a month.> is it dead? <Possibly a goner> sorry for not giving more info <No more info to give. It is said that without the right sized foodstuffs (usually seems to be a natural occurring type of food) most clams last for a year or less in a tank. What I take from that, is that clams need to be fed at some level. There just isn't enough nutrition derived from photosynthesis. Something to keep in mind. Check Barry out!! -Paul> 

Bleached spot on clams mantle- 5/28/03 G'day guys, <cheers, mate> Just a few quick questions regarding thistles and a clam. <and I will counter with a question right off the bat: what is a thistle? The common name is not familiar to me, my friend. I browsed several Australian message boards too (keyword searched) wondering if the name was colloquial and came up empty <G>. Tell me more about what kind of organisms this is, please> Firstly the clam in my tank has grown considerably over the past 6 months. <often so... as much as 5-10 mm monthly is not unheard of for T. derasa and T. gigas in particular> A small area on a flap has lost its pigment from brown speckled to white. Is this to do with this area not getting the light?? <not likely... or not a good sign if so. It seems surprising that any tissue lies settled on any single part of the mantle long enough to cause such a condition. Do you have enough current to keep the mantle of this clam (as with coral polyps) flowing nicely? If so... we need to seek another explanation> As this area is actually hidden when the clam is fully opened. When it shuts you can notice the white section which is only 2cm. Any advise as it doesn't seem to effect the clam but takes away some of the beauty. <it can/will be a problem in the long term though. Beyond current, aged lamps (or those with salt creep, dust, dirty lenses, etc) suffer the clams as the light degrades... the weakest parts of the mantle in turn are the first to show signs of stress/bleaching> Lastly thistles seem to be hard to keep in an aquarium. Why is this and what are the ideal conditions for it to survive. e.g.: placement in the tank and food sources etc?? Thanks Stu <as per above on the thistles, my friend. Kind regards, Anthony>

"Gaping" Squamosa - 4/2/03 Hi there WWM Crew... <Hi there. Paul here for a few> I hope this email finds you happy and healthy today. <Actually no, I have a horrible cold. A little slow on the draw, but otherwise fine> I have a question regarding the well being of my new T. Squamosa. <OK. Go for it>  Is it normal for them to gape for the first few days following acclimation? <Well, in my experience they can "gape" anytime and usually recover. You just never know though. If I remember though it seems to me that Squamosa kinda "gape" anyway.>  The lil guy was delivered Tuesday and was acclimated over a period of an hour plus. <Well, nice but did he go into an acclimation tank? In any event sounds fine>  I ensured that I added some tank water, via a turkey baster, over and over until the container was full. <very well>  I then dumped half and did the process over again.  After more than an hour, I finally placed him on a piece of empty clam shell just under the substrate for him to become accustomed to his new environs. <Very good. Lights off?>  Other than a troublesome wider inhalant, it seems okay.  Color is good and mantle expansion seems normal for a newbie. <Sounds about right> The packaging from the seller was wonderful. <Who is the seller if you don't mind me asking?> Many air filled bags of insulation surrounded the live specimen bag. <Cool>  There was 2 inch foam lining the box and two heating pads therein. <Good> The water temp was not all that cold, considering it is New England. <What does that mean?> I waited at the door all morning for delivery and acclimated it right away. <Very responsible>  It was en route for a short period of time (Next state overnight - FedEx) <Still could be a lot of handling between seller and buyer> The reason I chose Squamosa is that I have power compacts. <Ahh, good choice then> Everyone I speak with says that my 6w/per gallon should be sufficient. <Definitely>  I've read the book "Giant Clams" and it too says that Squamosa would be my choice. <Very good. Glad to hear you on board as a Conscientious Marine Aquarist> I was planning leaving him on the substrate, but your opinion on this is appreciated as well. <I would leave him there for about a week minimum. Then slowly start moving him toward his final resting place. In the wild though, these guys are usually found on the substrate. So he may be fine where he is. If he continues to gape though I would definitely hold off on moving him anywhere. Clams have been known to crash and die in about 12-24 hour period, so keep an eye on him. Oh yeah, definitely let the seller know he came to you in this "gaping" condition. From the picture though he looks pretty good!> I may just be paranoid.  Others have told me that Squamosa have larger siphons as compared to other Tridacnids. <True> I'm used to seeing Maximas which rarely "open wide". <Also true. Healthy ones anyway> I've attached a picture for your viewing. <Looks good>  You can email me direct if this is not FAQ worthy. Definitely FAQ worthy. Did you get a chance to read our FAQs? Lots of good info there. you can always contact Barry Neigut at ClamsDirect.com as he has quite a good amount of experience in the various hobby clams.> Thanks for all your help. <My pleasure David. I am sure your clam will thank you for your research as well!> David  

Clam exudation 3/27/03 Greetings!  I have a blue Tridacna maxima, about 5 inches below the surface of the water under a 175W MH with 40W of fluorescent actinic.  The clam is about two years old.  Recently I have noticed that in the evening, I see a very thin brown strand of  (I assume) Zooxanthellae algae coming out of the exhalant siphon.   <could be... sometimes they are expelled naturally in small packets, other times induced by stress (increase in light as with new bulbs or clarity as with water change or sudden use of carbon)> The clam is well extended and looks great.  Water parameters are great and unchanged, except that I recently (1 month ago) noticed that the pH was dropping to 8.00 during the night.  I slowly used Reef Buffer to raise the pH to about 8.45 during the day, dropping to about 8.30 at night.  Salinity is 1.025 and nitrites are zero, and nitrates are 5ppm.   <all good> I use PolyFilter and an Urchin Pro.  Is this algae discharge normal? thanks tom <likely no worries at all. Be mindful not to overfeed (at risk of clogging gills) with liquid supplements too. Best regards, Anthony>
Re: Clam exudation 3/27/03
Thanks for your response, Anthony.  I have been feeding liquid food, perhaps a little bit more than usual.  This afternoon I noticed some bleached spots on the mantle which weren't present this morning.  The mantle is open/out. <not good signs at all... and rules out coagulated food from overfeeding as the primary. Stress from a physical parameter is more likely now... the sudden influx of a larger than normal bit of freshwater perhaps for belated evap top-off? Dosing supplements in strong concentration near it at the top of the tank (sans dilution in sump or strong stream). Hmmm... many possibilities. Predation is more common in general but would not expectedly cause the bleach spots. Instead we are looking for stress or disease here. Perhaps a new fish or coral added recently without QT brought in a pathogen> Any suggestions? thanks, tom <watch nightly for predators, but otherwise do not disturb while evaluating water quality. A water change is usually helpful too (dilution of the unknown). Anthony>

I Have a Question About a Clam Hi Bob or whoever is taking your place if your not there; <Steven Pro right now.> I've never had a clam before but I'm curious about something I saw on all the clams I have been looking at in the local stores. I believe based on research that these clams are Tridacna derasa. I understand that each has its "mouth" but I'm curious because most of them seem to have a split on the other side of the clam. Is this normal? <Yes, clams have both an inhalant siphon and an exhalent siphon.> Are these clams in distress? <Nope> Do they all get this split? <Yes, what goes in must come out.> Are they forming another mouth? <No> Are these specimens to get or to avoid? <There are other factors to consider. Daniel Knop has written an excellent book, "Giant Clams". Please pick up a copy for your education prior to purchasing any clams.> Thanks, Mac <You are welcome. -Steven Pro>

Stressed Out Clams? Dear WWM Crew, Gentlemen, how are you?  <very well with thanks!> I need your professional advice once more; I hope you don't mind as I truly appreciate all your efforts/inputs to improve this hobby.  <thanks again... but it is not entirely altruistic: Bob pays us handsomely in chocolate malt balls> I have a few questions regarding my recently purchased squamosa clam and maxima clam. First, let me preface by giving you the conditions of my 90 gallon reef tank: lightning--powered by 2x-175 watt 10,000K metal halides and 130 watts of actinic PC, and water parameters--pH @ 8.3, carbonate hardness @ 10.5 dKH, salinity @ 1.025, calcium @ 400ppm, temperature is constant @ 78 degree, magnesium @ 1300ppm, ammonia @ 0ppm, nitrite @ 0ppm, and nitrates @ 2ppm. Fishes included are: yellow and purple tangs, and 3 flame wrasses. The two clams were purchased 3 days ago and they are both about 3.5 inches. They are placed at the bottom being acclimated to my lightning system.  <excellent... that was my first question in mind... Good move> I plan to move the maxima clam towards the middle of the tank at the end of this week and leave the squamosa clam at the bottom. Would this be a wise decision?  <because of adult sizes and likely light requirements, I would agree that this is reasonable> My concern with both of these clams is the wide opening of their incurrent siphon. It is more pronounced with the squamosa than the maxima and this occurrence only happens when the metal halides are on. <many theorizes for this...not all bad. Have you read Daniel Knop's Giant Clams book? Excellent!!!> When the metal halides are off and only the actinic PCs are on or the lights are completely off, the incurrent siphon is completely closed. Is this normal behavior?  <the predictability of it is reassuring but categorically it may not happen with all> Or should I be concern with predation, sickness, and/or accumulated stress from shipping?  <do examine closely (and periodically 4-6 times yearly or better) for tiny Pyramidellid snails> I performed the shading test, and the maxima is very responsive to blockage of light and the squamosa is less responsive.  < an unreliable test. Some like T. gigas hardly respond at all> This has led me to wonder about the correlation between the squamosa having a wider incurrent siphon opening and its slower response rate to the shading test as not being in good health.  <not necessarily> I have also checked for predation with a flashlight at night and I did not see any snails on the mantles.  <excellent> I feed DT's twice a week.  <hmmm... do read in Knop's book about feeding protocols and foodstuffs. Also, review past FAQs and archives on how best to feed such phytoplankton supplements unless you are already using a blender> Is there anything I do to help them? Any comments and/or input is greatly appreciated. <unfortunately the clam is not exhibiting any symptom that we may fairly act upon. Your system is very fine, and acclimation procedures quite considerate. It may simply be acclimation/adaptation or even nothing at all. Do not be attempted to move the clams at all for at least 2 weeks. Observe their behavior and follow up here if necessary. I suspect at the end of two weeks there will be no new news <wink> and all will be fine. Best regards, Anthony> Thank you, Dan

Derasa Clam problem.. Hello again, I am writing to you this time about one my Derasa Clams. I have had them both over 1 month and they have been looking fine. Both have been placed on the substrate in the middle of the tank. Today, I noticed that this one in particular, had receded it mantel way back into its shell and the mantle has started to separate from the shell. It does open and close occasionally. The other clam is doing well. I am using 96W PC lights from Custom Sealife(8800k daylight and 6700k actinic). I have plenty of water movement 1 Rio800, 2 Rio 180 and water moment from an AquaClear 300 and HOT magnum (both about 300g.p.h.). Water levels are temp = 76.6, PH = 8.1, Ammonia and Nitrite =0, nitrate = 2.2, dKH = 9.14, Calcium = 490, Phosphate = 0.  <Mmm, your calcium is a bit high...> All of my corals Euphyllia sp., leathers and plate corals are thriving. I have read through the FAQ's section on www.wetwebmedia.com <http://www.wetwebmedia.com/> and did not see any similar instances of this happening. Am I losing a clam or is there something I can do to save him?? <Even after a month, this specimen may simply be "settling in"... Do take a close look (especially at night with a flashlight) to ascertain whether "somebody" is bothering this clam... worms, snails... can be trouble. Bob Fenner> Regards, Keith Broadbent
Re: Derasa Clam problem..
Do you think he may not be getting enough light and to try moving him up higher on the reef?? <Hmm, possibly... worth trying. Bob Fenner> Regards, Keith Broadbent

Clam questions Bob, Thanks for you response. I have some additional questions though, - You mentioned it might be a lack of light, but I didn't think this was the case because the clams didn't overextend their mantle (as described in Knop's Giant Clams book), and they didn't show any bleaching that I would expect. I also tried a variety of placements in the tank - including placing small Maximas/Croceas (1") within 4 inches of the surface.  <Mmm, the placement is a valid indication, the non-extended mantles, bleaching not necessarily so> Also, the demise is sudden - the clams usually look healthy for 1 month or more, and then die within a week (usually within 5 days). Am I missing something in regard to light? <Not likely if the losses were rapid onset... more likely something amiss with chemistry (mis-supplementation in most cases) or an undiscovered parasite load of consequence (like Pyramidellid snails)> - You asked how I maintain water chem. I use SeaChem's Reef builder and Reef Advantage Calcium. I also use instant ocean salt. (I am in the process of converting one tank to a calcium reactor - Korallin). Is my use of SeaChem's products potentially involved in the demise of my clams? <Doubtful. No other additions?> - You discounted my thoughts on predation. The one thing that keeps pointing me in this direction is that I NEVER loose multiple clams at once. It's always one at a time. And then shortly (within 1-2 wks) after one dies, another one starts to show symptoms. Again, can you expand one why you don't think its predation? <Could be... In accounting for how many specimens lost this is just historically about third, fourth in line as common causes/categories of loss> - Do you have any idea of what the normal survival rates for maxima/crocea clams are when they are purchased from good mail-order firms (FFExpress, and others): <Just guesses... such data are rarely recorded, never shared in the trade> 1) the small ones (1" and under) 2) medium (1 - 3") 3) large (3+ inches) <Hmm, I would state with certainty that "larger ones live longer"... And guess that one inchers on mean/average probably only make it a month, 1-3" probably 2-3 months (most are "killed off"), 3" ones probably 4-6 months... Some folks do keep any/all sizes for years... but most "don't make it"> The reason I ask is I'm trying to get an idea of what constitutes 'Success'. <My friend this is beyond us! "Smiles per hour"? Reproducing? Closing the loop, having tank bred young grow up, in turn producing viable young? A subjective measure, the affective domain... "how you feel"?> I haven't had much luck with long term clam survival (except for my large and indestructible derasa), but from what I've seen, the LFS's don't seem to have much luck either. <Some sources, lines are decidedly much better than others... Much has to do with how these animals are kept, treated "intermediately" going from almost wild culture facilities through holding/shipping... Need TLC at this crucial junction... intense lighting (likely MH), foods, feeding, addition of biomineral, alkaline materials... Only know of three outfits out of dozens that provide this level of care... their clams are healthier, on "average" live longer/better> - You mentioned phosphates (and Knop indicates nitrates are needed) for clam health.  <Yes, actually for all life on this planet.> My kits have always registered 0 phos/nitrate. Should I be 'injecting' phosphates/nitrates into my tank (gosh - this is tough to swallow, given the effort I went to eliminate them). <Mmm, regularly exogenous (outside, provided) feeding of your livestock should present enough of these... do you have too vigorous "other" transport mechanisms? Like chemical filtration, too much macro-algal growth...?> I have Red-Sea Berlin classic skimmers running on both 75 gal tanks, with 100+ lbs of Fiji LR and planted/lit sumps.  <Might try trimming back the macrophytes in the sump> This combo seems to bring nitrates/phosphates to immeasurable levels, at least with my test kits (nitrates under 2.5 ppm, phosphates under 0.05 mg/l). I'm sure there are some levels of nitrates/phosphates though, because the macro algae - Caulerpa - in my sump grows well. - any other suggestions on what I could try to increase my survival rates, or what could be the cause? Thanks again - and apologies for the long note. <We will be discussing this... nature further. Bob Fenner>

Just lost a Derasa and a Maxima Hi Bob, <Yikes, what happened?> I feel so sad that I just lost two / all of my clams, one Derasa and one Maxima. I have had them for 9 months and a year respectively .. both died within a week apart. I first notice something is wrong when they wouldn't open that much, tried to adjust lighting, but the shrinking continued and then both were in some sort of "gaping" position until I removed them. I noticed they both seem to have lost their legs and that it looked very hollow bottom up. <Hmm> I am a little puzzled and very concerned with the clam losses. If you remember, I am in the middle of battling Cyano and looking up my log, I setup a refugium with macro algae and took out the HOT with AC and phosphate sponge 2 weeks ago. Other than that, everything else have remained the same. Do you think they died from poisoning from the macroalgae (there has been no dying though)? <Doubtful> Or is there some sort of a "predator"?  <If they were "hollow" inside it may be so... Pyramidellid snails, some Polychaete worms can eat Tridacnid clams quickly in numbers> I added the Kent buffer to boost alkalinity over the last 2 weeks, from 6.8 to 11.2 then 12.5 over 2 weeks. <Mmm> My parameters are: 60G reef, Ph 8.0, NO3 2.5, PO4 <0.03, Alk 12, Ca 400, temp 80-82F, 45lbs LR, 1-2inch sand. Livestock: flame angel, yellow tang, damsel, goby, bubble corral, frogspawn, flowerpot, mushrooms, sun corals (all arranged at a distance from one another), cleaner shrimp, Astrea and hermits. Thanks. Brian <There was nothing left of the clams? Very strange, as in disturbing. Bob Fenner>

Tridacna clams I have a 125g reef that has been going for one year. The six fish all seem healthy along with an extremely large and happy bubble coral I've had for four years. I have numerous other corals that are in good shape also. I have two 175w halide lights. In the last four weeks all three of my Tridacna sp. have died. They looked good for a few months then started to gape. My nitrates are high (greater than 10ppm nitrate nitrogen). Is this the problem? Thanks, George >> Wow, and sorry to hear of your clam losses... I doubt if the nitrates had much to do with their demise. Some folks who culture them have much, much more nitrate in their water... some on purpose/by design. So what does account for their deaths? Not much clues in this email... the Plerogyra (Bubble Coral) is doing fine... enough light... Are you "supplementing" your system chemically? This is the usual, or most common cause of Tridacnid loss... Any chance a predator is involved? Did you note any "chew" marks on the clams mantles or other soft body parts? Do you know what Pyramidellid snails look like? How long were the clams "gaping" before perishing? Did they go all at once? Which died first, largest, smallest, species... Bob Fenner

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