Someone just asked me about these guys again on Aqualink, and I couldn't find my detailed response from the past in the archives of either board, so I thought I'd post it again in the hopes that I'll never have to type this out again 
Unfortunately the software still seems to have a couple of bugs and won't let me add certain links to the post no matter how I try, so I'll have to skip them...
I'm going to guess from your description here that you are talking about one of the "flameââ"šÂ¬Ã‚ or ââ"šÂ¬Ã…"œflashing scallopsââ"šÂ¬Ã‚ Lima spp. Although these animals are called "scallops" they are not related to scallops by anything other than appearance, and are really file clams (scallops swim "forwards" while clams swim "backwards"). Flame and flashing "scallops" have a very poor survival record in aquaria, and the typical pattern of the animals hiding, and slowly wasting away (over a few to about 6 months) is the norm for these animals. The single most common cause for their demise in aquaria, I would guess, is starvation. Although I should also point out that these animals are pretty short-lived (estimates usually run about 3 years), and with the gaining popularity of feeding reef aquaria phytoplankton, I have now heard a couple of reports of the animals living for a year or so in captivity.
Another factor to consider is that these animals are protandrous hermaphrodites, and small individuals (~2.5-5 cm shell height) being predominantly male, and large individuals (~5-7.5 cm shell height) being predominantly female, so if you have any intent to try to breed them, youââ"šÂ¬Ã¢"žÂ¢ll need a range of sizes, and it is worth keeping in mind that getting a male will mean that youââ"šÂ¬Ã¢"žÂ¢ll have a chance of keeping the animal alive for a few years...
These animals are specialist filter feeders that require a *lot* of planktonic food. These animals feed entirely on phytoplankton and tiny zooplankton (<1/10th of a mm -- much smaller than newly hatched brine shrimp), and without heavy supplements, no reef tank produces enough of these foods to support a decent-sized filter feeder like this. The majority of their food by number is usually phytoplankton in the 5-40 micrometer (um) range (1/25 to 1/200th of a millimeter), but invertebrate larvae (up to a maximum size of 200 um -- 1/5th of a millimeter) are preferred if the animals are offered a choice, and these tiny zooplankton are likely the primary source of energy intake for the clams in the wild.
In most filter-feeding species, the addition of phytoplankton along with the presence of the tiny zooplankton (the primary zooplankton in this size range are rotifers, and invertebrate larvae) increases the rate of feeding (although this does not seem to be the case with Lima, which Iââ"šÂ¬Ã¢"žÂ¢ll explain below), so it is almost always a good idea to feed both phytoplankton and tiny zooplankton (like rotifers) to the tank at the same time if you plan to keep any filter-feeding animals. At least some clams and oysters actually seem capable of selecting particles directly by their surface flavor (which is probably why pea flour and yeast-based aquarium products fail so often at keeping these animals live), and flame ââ"šÂ¬Ã…"œscallopsââ"šÂ¬Ã‚ seem to be among them, rejecting the majority of food typically offered in an aquarium, as many people have observed.
In laboratory feeding experiments, researchers found that inert plastic beads of the size of phytoplankton (5-40 um) were ingested at the same rate as the phytoplankton themselves, suggesting that the animals are incapable of excluding tiny particles regardless of taste. However, inert beads the size of invertebrates larvae (100-200 um) were rejected by the clams, and given that it has traditionally been difficult to obtain food even this small, it is not surprising that success rates with these animals has been so low. Unlike most studies of invertebrate filter-feeding, addition of phytoplankton to the medium did not affect the ingestion rate of the larger (100-200 um), and in this case, the animals actually seem capable of selecting particles directly by their surface flavor; this is probably why pea flour and yeast-based aquarium products fail at keeping these animals alive, and we have actually done demonstrations for students in our Invertebrate Zoology classes here of the animals rejecting pea flour and yeast-based invertebrate foods. The primary prey of the animals were invertebrate larvae, and ~75% of larvae on average were consumed by a clam in a given feeding trial (because they become so dilute in the culture jars after that point that the clams canââ"šÂ¬Ã¢"žÂ¢t pump enough water to catch the last few).
In any case, a good diet of mixed phytoplankton and enriched rotifers ought to be appropriate for keeping these animals, but I would suggest staying away from the typical rack of bottled "invert foods" at the local petshops, which typically contain high concentrations of dissolved organics, and rarely contain particles of the correct size and ââ"šÂ¬Ã‹Å“flavorââ"šÂ¬Ã¢"žÂ¢ (for lack of a better word) that would be acceptable to Lima.
If you are not feeding a lot of phytoplankton and rotifers on a regular (at least every second day) basis, your clam is going to starve to death, and no matter how cool you think the animal is, you should not add one to your aquarium. If you are willing to start feeding phytoplankton (which has recently become readily available through vendors such as DTââ"šÂ¬Ã¢"žÂ¢s, BSD, LiquidLife, etc...) and could be convinced to start culturing rotifers to feed as well (e.g., I have an article on the biology and culture of rotifers in the Aquarium.Net archives that the system refuses to link to normally for some reason -- the url is http://www.aquarium.net/0397/0397_5.shtml), then it may be possible for you to keep one of these clams in an aquarium. The availability and ease of feeding Rotifer Pearls may also increase chances of survival of these animals, but I have not personally tried to feed with them, and simply do not know whether or not the clams will readily accept these as surrogate invertebrate larvae...
Another important consideration is that flame "scallops" are pretty reclusive by nature, and part of the reason I think so many people fail with them (aside from the diet issue above) is that they force the animals to stay where they are visible (or keep moving them back to the front where they are "supposed to be"). The clams prefer a deep crevice in which they can hide and gain some measure of protection from predators, against which they have very few defenses. Most bivalves escape predation by having tightly closing valves and a special type of muscle that allows them to "lock" the valves closed. Lima lacks those adaptations, and is easily preyed upon by "wimpy" stars that would not be able to eat a green mussel of equivalent size, so predation is more of an issue for these clams than for most bivalves. Many people have reported that some sea star in their tank has eaten their scallop, and that is why I think that, in general, keeping stars out of a tank with these clams is a good idea, but I suspect that the stress of keeping the clams out in the open takes it's toll on most of them, and the stars simply move in to finish off an easy meal when the clams stop resisting. My guess is that this problem derives from the stress caused by placing these animals out in the open for easy viewing. Because they are easy prey, and prefer deep crevices into which they can retreat, they will continue to move away from an easily accessible and viewable spot (much to the chagrin of the aquarist), and that takes a lot of energy from the animals (they are not all that motile to start with). If they are getting limited or insufficient food in the first place, and then placed into a stressful situation in which they continually have to expend an enormous amount of energy, it is not at all surprising that the animals frequently die...
All of these factors need to be taken into consideration if you plan to add a ââ"šÂ¬Ã…"œflame or flashing scallopââ"šÂ¬Ã‚ to your tank, and if you are not prepared to feed them properly and allow them to crawl back into the rock-work to a place that makes them difficult to view, but where they will feel comfortable and remain for the long-term, then you should certainly not consider purchasing one of these animals...
Rob
Unfortunately the software still seems to have a couple of bugs and won't let me add certain links to the post no matter how I try, so I'll have to skip them...I'm going to guess from your description here that you are talking about one of the "flameââ"šÂ¬Ã‚ or ââ"šÂ¬Ã…"œflashing scallopsââ"šÂ¬Ã‚ Lima spp. Although these animals are called "scallops" they are not related to scallops by anything other than appearance, and are really file clams (scallops swim "forwards" while clams swim "backwards"). Flame and flashing "scallops" have a very poor survival record in aquaria, and the typical pattern of the animals hiding, and slowly wasting away (over a few to about 6 months) is the norm for these animals. The single most common cause for their demise in aquaria, I would guess, is starvation. Although I should also point out that these animals are pretty short-lived (estimates usually run about 3 years), and with the gaining popularity of feeding reef aquaria phytoplankton, I have now heard a couple of reports of the animals living for a year or so in captivity.
Another factor to consider is that these animals are protandrous hermaphrodites, and small individuals (~2.5-5 cm shell height) being predominantly male, and large individuals (~5-7.5 cm shell height) being predominantly female, so if you have any intent to try to breed them, youââ"šÂ¬Ã¢"žÂ¢ll need a range of sizes, and it is worth keeping in mind that getting a male will mean that youââ"šÂ¬Ã¢"žÂ¢ll have a chance of keeping the animal alive for a few years...
These animals are specialist filter feeders that require a *lot* of planktonic food. These animals feed entirely on phytoplankton and tiny zooplankton (<1/10th of a mm -- much smaller than newly hatched brine shrimp), and without heavy supplements, no reef tank produces enough of these foods to support a decent-sized filter feeder like this. The majority of their food by number is usually phytoplankton in the 5-40 micrometer (um) range (1/25 to 1/200th of a millimeter), but invertebrate larvae (up to a maximum size of 200 um -- 1/5th of a millimeter) are preferred if the animals are offered a choice, and these tiny zooplankton are likely the primary source of energy intake for the clams in the wild.
In most filter-feeding species, the addition of phytoplankton along with the presence of the tiny zooplankton (the primary zooplankton in this size range are rotifers, and invertebrate larvae) increases the rate of feeding (although this does not seem to be the case with Lima, which Iââ"šÂ¬Ã¢"žÂ¢ll explain below), so it is almost always a good idea to feed both phytoplankton and tiny zooplankton (like rotifers) to the tank at the same time if you plan to keep any filter-feeding animals. At least some clams and oysters actually seem capable of selecting particles directly by their surface flavor (which is probably why pea flour and yeast-based aquarium products fail so often at keeping these animals live), and flame ââ"šÂ¬Ã…"œscallopsââ"šÂ¬Ã‚ seem to be among them, rejecting the majority of food typically offered in an aquarium, as many people have observed.
In laboratory feeding experiments, researchers found that inert plastic beads of the size of phytoplankton (5-40 um) were ingested at the same rate as the phytoplankton themselves, suggesting that the animals are incapable of excluding tiny particles regardless of taste. However, inert beads the size of invertebrates larvae (100-200 um) were rejected by the clams, and given that it has traditionally been difficult to obtain food even this small, it is not surprising that success rates with these animals has been so low. Unlike most studies of invertebrate filter-feeding, addition of phytoplankton to the medium did not affect the ingestion rate of the larger (100-200 um), and in this case, the animals actually seem capable of selecting particles directly by their surface flavor; this is probably why pea flour and yeast-based aquarium products fail at keeping these animals alive, and we have actually done demonstrations for students in our Invertebrate Zoology classes here of the animals rejecting pea flour and yeast-based invertebrate foods. The primary prey of the animals were invertebrate larvae, and ~75% of larvae on average were consumed by a clam in a given feeding trial (because they become so dilute in the culture jars after that point that the clams canââ"šÂ¬Ã¢"žÂ¢t pump enough water to catch the last few).
In any case, a good diet of mixed phytoplankton and enriched rotifers ought to be appropriate for keeping these animals, but I would suggest staying away from the typical rack of bottled "invert foods" at the local petshops, which typically contain high concentrations of dissolved organics, and rarely contain particles of the correct size and ââ"šÂ¬Ã‹Å“flavorââ"šÂ¬Ã¢"žÂ¢ (for lack of a better word) that would be acceptable to Lima.
If you are not feeding a lot of phytoplankton and rotifers on a regular (at least every second day) basis, your clam is going to starve to death, and no matter how cool you think the animal is, you should not add one to your aquarium. If you are willing to start feeding phytoplankton (which has recently become readily available through vendors such as DTââ"šÂ¬Ã¢"žÂ¢s, BSD, LiquidLife, etc...) and could be convinced to start culturing rotifers to feed as well (e.g., I have an article on the biology and culture of rotifers in the Aquarium.Net archives that the system refuses to link to normally for some reason -- the url is http://www.aquarium.net/0397/0397_5.shtml), then it may be possible for you to keep one of these clams in an aquarium. The availability and ease of feeding Rotifer Pearls may also increase chances of survival of these animals, but I have not personally tried to feed with them, and simply do not know whether or not the clams will readily accept these as surrogate invertebrate larvae...
Another important consideration is that flame "scallops" are pretty reclusive by nature, and part of the reason I think so many people fail with them (aside from the diet issue above) is that they force the animals to stay where they are visible (or keep moving them back to the front where they are "supposed to be"). The clams prefer a deep crevice in which they can hide and gain some measure of protection from predators, against which they have very few defenses. Most bivalves escape predation by having tightly closing valves and a special type of muscle that allows them to "lock" the valves closed. Lima lacks those adaptations, and is easily preyed upon by "wimpy" stars that would not be able to eat a green mussel of equivalent size, so predation is more of an issue for these clams than for most bivalves. Many people have reported that some sea star in their tank has eaten their scallop, and that is why I think that, in general, keeping stars out of a tank with these clams is a good idea, but I suspect that the stress of keeping the clams out in the open takes it's toll on most of them, and the stars simply move in to finish off an easy meal when the clams stop resisting. My guess is that this problem derives from the stress caused by placing these animals out in the open for easy viewing. Because they are easy prey, and prefer deep crevices into which they can retreat, they will continue to move away from an easily accessible and viewable spot (much to the chagrin of the aquarist), and that takes a lot of energy from the animals (they are not all that motile to start with). If they are getting limited or insufficient food in the first place, and then placed into a stressful situation in which they continually have to expend an enormous amount of energy, it is not at all surprising that the animals frequently die...
All of these factors need to be taken into consideration if you plan to add a ââ"šÂ¬Ã…"œflame or flashing scallopââ"šÂ¬Ã‚ to your tank, and if you are not prepared to feed them properly and allow them to crawl back into the rock-work to a place that makes them difficult to view, but where they will feel comfortable and remain for the long-term, then you should certainly not consider purchasing one of these animals...
Rob
