Retracted clam showing signs of mantle discoloration

Discussion in 'Clams' started by Dr. Bergeron, Aug 21, 2010.

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  1. Dr. Bergeron

    Dr. Bergeron Peppermint Shrimp

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    Lake Worth, FL
    Hi everyone, I have sort of a brain buster here....

    We've had a T. Crocea in our tank for 6+ months now and it's been doing great. Recently, it has been closed up, and ultra sensitive/overly suspicious of movement in the tank. It's also been closing up tight quite frequently, and instead of opening with a nice floppy mantle, it's been half closed with only a bit showing. I've noticed the sides of the mantle are starting to become slightly discolored. I'm assuming due to lack of light from being closed all the time but could it be something else? I'm sort of at a loss here as to what could be wrong. I've read that from time to time clams will close up more and be finicky, but this has been going on longer than 10 days now and I'm starting to worry.

    The only thing that is new to the tank is an orchid dottyback. However, I haven't heard of these fish to be clam killers, nor have I seen it bother or show any interest in the clam at all. Think this fish could be secretly attacking the clam?

    Parameters are standard for my tank, and nothing is out of the ordinary.

    I've also noticed, now that the clam has been closed up, that there's a very healthy white ridge of growth around the outside of the shell. Everything about the clam says it should be healthy, but it's not acting like it.

    I think kcbrad had a similar experience but mine doesn't seem to be showing any progress and is getting more and more skiddish, not better.

    Anyone go through this before, and is there anything I should be looking for? I am almost tempted to make an acrylic box for the clam with holes in it, to see if it really is the dottyback bothering it.

    I'll see if I can get a pic of the clam later this weekend.

    Thanks for any suggestions you can give!
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  3. cuttingras

    cuttingras Starving Artist :)

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    Hey, This is a great article on clams, you may have read it already but it's worth another look...

    It's from Reefkeeping.com


    Aquarium Care

    As you’d probably expect, water quality requirements for keeping croceas fall right in with what’s generally considered “standard” for reef aquariums. Temperatures between 25° and 28°C are optimal, as is a pH of 8.1 to 8.3. Alkalinity should optimally be kept in the range of 9 to 12dKH , and calcium should be maintained at 380 to 450ppm. About the only thing in particular to note is that as a clam grows, it adds new shell material to the entire inner surface of its valves, not just their upper margin; so even a slow growing crocea can use more calcium than you might expect, and having several in an aquarium can deplete calcium and alkalinity surprisingly quickly.
    Other than that, sufficient lighting is really the key to keeping them healthy. Light falling upon the mantle and the zooxanthellae kept inside it is the primary means by which croceas get their energy in the wild, and the same goes for their life in aquariums. So, you absolutely must give them sufficient lighting if you expect to keep them alive.​
    Croceas live at shallower depths than other Tridacna species, where they receive intense light; so they require more light than the other species when kept in aquaria. And, on top of species-level differences, there’s also variability between individuals. Genetic differences can make one clam more fit than another under the same conditions; two individuals may be carrying different strains of zooxanthellae, and so on. This is very important to remember, as you always want to provide at least enough light to keep the average clam of a given species alive, not the minimum that you think an individual of the species could possibly live under. ​
    In the case of crocea, fluorescent lighting will suffice only in very shallow tanks, or if a specimen is placed near the water’s surface in a deeper tank. I highly recommend squeezing as many bulbs into the canopy/fixture as possible, mounting the bulbs so that they are as close to the water as possible (without causing heat problems), and then placing the specimen within 20 or 30cm of the water’s surface, preferably less. Some specimens may be able to get by at times with less light, or further down in deeper tanks, but I implore you not to take chances. Metal halide lighting is really the way to go, preferably a combination system comprised of metal halide and fluorescent lighting. ​
    Using a metal halide system allows you to place a crocea deeper into a tank, which also makes it easier to view. Most of them look their best when viewed from a high angle, so they actually look much better when placed near or on the bottom of a tank. A standard 175-watt metal halide bulb should be sufficient for keeping a crocea on the bottom of any small- to medium-sized tanks, as in anything less than 45 or 50cm deep (or no deeper than this in a larger tank). But, I’d go ahead and move up to 250-watt, or even 400-watt, bulbs if a specimen will be any further than that from the surface.​
    Next, we get to feeding (or not feeding). All tridacnids are filter-feeders that ingest a variety of particulates they strip from surrounding waters. However, their zooxanthellae can provide a great deal of their nutritional needs, and they also can absorb nutrients directly from seawater. In fact, if provided with enough light, croceas of any size can completely forgo filter feeding and can thrive in particulate-free water as long as enough dissolved nutrients are present.
    I dedicated an entire chapter to tridacnid nutrition in Fatherree (2006), which covers how they “work” in great detail, but I’ll keep it simple here by saying that, in aquariums, basically everything is taken care of by having good lighting and simply feeding the fishes. Some fish food is left uneaten and becomes detritus, which croceas can filter out, and detritus also releases other nutrients into the water as it decomposes. But, most food is eaten by the fishes, which then give off dissolved nutrients (ammonia, in particular) and excrete solid wastes that can also become detritus. So, when you feed the fishes, you’re feeding the clams as well.​
    The real question is whether or not there are enough fishes in your aquarium, and/or enough fish food going into your aquarium, to support one or more tridacnids. It is, indeed, possible to have too low a fish load (or too high a clam load, depending on how you look at it) in a tank, which means that the amount of fish waste produced is not enough to support the needs of the clam(s). My advice, then, is to refrain from taking any chances and to use a quality phytoplankton product if you have any doubts. Again, though, the vast majority of hobbyists do not need to do so.​
    Then there’s water flow to consider, because croceas live in shallow waters on reefs and near-reef environments, and therefore are regularly exposed to strong currents and wave activity. Water movement in aquariums, however, is typically nothing like that on the reef or nearby, as the flow in most aquariums tends to be quite linear and constant. In most tanks a pump outlet might blast water in one particular spot day and night at about the same volume per minute, and rarely creates any real surge or turbulence. Although it’s perfectly fine to expose croceas to a low velocity surge, or to turbulent flow, putting them in a position where a pump just blasts them with a strong, non-stop linear current is not recommended. Basically, any sort of current that causes the mantle to fold upward too much, or over onto itself all the time, is bad, as is any current that makes a specimen chronically retract its mantle. Thus, you can put a clam anywhere you like with respect to current, as long as it doesn’t elicit either of these reactions. Yes, a crocea can take an occasional blasting that folds it up or makes it retract, but if this happens all the time, the clam can suffer from stress, or may even begin to starve from lack of light due to lessened mantle extension.​
    Finally, we get to placement. I think it’s best to place any species on the same sort of substrate that you’d find it living on in its natural habitat, and croceas are never found on sand. I’ve never found one living on rubble, either; they live on (in) hard substrates only. So, a crocea should be placed on a solid substrate, if at all possible, where it can attach itself firmly to one spot as it would do in the wild. A flat piece of live rock or coral skeleton works very well, but a piece of tile can also be used. It may take anywhere from a few hours up to a couple of weeks, but a healthy clam will usually attach itself with at least a few byssal threads, or maybe many. I’m not suggesting that you absolutely must to do this by any means, but I do recommend it.​
    [​IMG] [​IMG]
    Croceas normally reach out of the bottom of their shell and form an attachment using a number of tough byssal threads. Here you can see the foot (left), which contains the byssal organ, reaching out from a crocea and forming some fresh byssal threads (on the shell of a neighboring clam, in this case).​
    Keep in mind that if you don’t like the way it looks to have your clam attached to and sitting on top of a rock, you can always wait for it to attach to whatever you put it onto, then bury that piece. It’s not a problem to bury a rock, or whatever else it attaches to, just under the surface by covering it with a bit of sand or gravel. However, you shouldn’t overdo it in such a way that the bottom part of a clam is down in the sand, as it can be irritated when it opens its shell if any of the grains manage to get inside.​
    Okay, with all that stuff covered, now let me tell you about some of the things that you should not do when it comes to the placement of a specimen. Don’t place a crocea in a tight crevice between rocks and such; this may restrict its ability to open fully, and also increases the risk of it falling down into the rockwork if it moves around too much. Don’t put one in a hole in a rock that might restrict its ability to open fully, either. And, if you do place one in a large enough hole, never let a lot of detritus settle into the hole around the clam. You should blow out any buildup of crud by using a turkey baster, powerhead, etc. ​
    If a specimen has attached to a piece of rock, shell, etc., never try to move the clam and the piece by grabbing the clam. That’s a good way to injure it; you should always pick up the clam and the piece together, and be very careful when handling the two. Likewise, you should never try to pull a crocea off anything that it’s attached to because you can rip the byssal organ out of it. Finally, don’t move one repeatedly over a short period of time. It can be stressful enough trying to adapt to changes in lighting and current when its moved into an aquarium, and quickly moving it from one place to another to another can sometimes be too stressful. Such activities can lead to slowed growth or a greater susceptibility to disease due to stress, or can even outright kill them. If you must move one around/up, be sure to give it plenty of time between each move, as in a week or two at the least.
  4. Dr. Bergeron

    Dr. Bergeron Peppermint Shrimp

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    Just as an update on this. I caught the offender red handed trying to eat the clam's mantle.

    Bi-color blenny! What a jerk! Weird that after months and months of being in the tank with the clam he would suddenly try to much on the clam. For now I have a tomato basket over the clam protecting it until I decide what to do with blenny.
  5. 2in10

    2in10 Super Moderator Staff Member

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    Glad you caught the reason, but sorry to hear one of you animals is the culprit.
  6. coral reefer

    coral reefer Giant Squid

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    When a clam closes up that is normally a sure sign that there is a problem because clams are not meant to remain closed as this requires alot of energy.
  7. WhiskyTango

    WhiskyTango Torch Coral

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    Funny bro, yesterday I was in a coffee shop talking with a buddy who's also a reefer, and he was telling me about his fully grown bi-color that just destroyed his blue maxima. I had no idea. I thought bi-colors were just harmless run of the mill algae eating blennies. I guess not.
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  9. Mainstream Aqua

    Mainstream Aqua 3reef Sponsor

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    bi colors can be hit or miss. Most of the time they are okay but you never know. I have had several over the years and when I first got into the hobby, I had an itch for blennys. Combine their aggression and appetite, you have yourself a little curious, wormy, coral nipping, clam craving fish.

    All fish are really hit or miss when we are thinking of it like that. I have a blue hippo tang in my 120g reef that will eat a wellso up as soon as I put it in there. However, I also have a flame angel fish in there that has not even though about touching any LPS and barely nips and acros.