How to Choose Healthy Giant Clams

[damien]

Tridacnid clams — and clams in general — have a much more complex physiology than corals. Their ability to regenerate damaged tissues or organ systems is much more limited, and, unlike a soft coral, a clam often cannot recover from damage caused by unsuitable environmental conditions.

So, we must use caution when choosing a clam from an aquarium store. Here are a few hints that will help you in making sure that a clam is healthy and has been kept under suitable conditions. More detailed information about this important topic can be found in the chapters “Buying Clams in the Pet Shop” and “Clam Diseases” in my book Giant Clams (Knop 1996).

If you are interested in a particular clam and plan to purchase it, you should first look at the stocking conditions of the store in general. Is the lighting sufficient and of the right spectral composition? Even a few days with unsuitable lighting will stress the clam’s adaptation mechanisms. Is the water quality sufficient? Is there foam fractionation? Next, look for empty pairs of shells in the tank. If there are a lot of them in the stocking tank, in neighboring tanks, in a sump or any other place in the store, while this does not necessarily say anything about the health of the clam we have chosen, it might give us an indication about this particular store’s success in keeping tridacnid clams, as well as the condition of the recent clam shipment that included the clam we have chosen. Many retailers import clams directly, and if a clam shipment arrives in bad condition there are often lots of empty shells.

If the clam has been imported very recently (a few days before) you should wait a few more days before purchasing it. During the first two weeks after shipping, clams are still undergoing an adaptation period, adjusting to their new environment. If possible, the clam should not be placed in yet another new tank environment during this period.

The most visible indication of the health of a tridacnid clam is the incurrent syphon. This slit-shaped opening should be closed most of the time. Normally, clams open it just for a short period of time. If the incurrent syphon is wide open or “gaping” (Sprung and Delbeek 1994), the clam is probably in a weakened state, caused most likely by the stress of shipping. This condition sometimes disappears after a few days, but the percentage of losses is quite high among these “gaping” clams, so they are best avoided.

Another obvious sign of health in tridacnid clams is the reaction of the clam to being shaded. If we block the illumination by holding a hand between the light and the clam, the syphonal mantle should partially retract spontaneously. This is a natural protective mechanism — if the clam is in a weakened state, it might occur slowly or not at all.

If the clam of your choice has a good reaction to having its light blocked, and the incurrent syphon is not “gaping,” the next thing to look for is bleaching or fading spots on the syphonal mantle and parasites/predators on the shells. The most common predators on tridacnid clams are the pyramidellid snails. These tiny, white-shelled snails sometimes spend the daytime on the upper shell margin of the clam, but mostly they hide on the bottom of the shell during the day. At night they travel up to the syphonal mantle and suck the blood with the help of their tussel (Knop 1996). Because they readily propagate in a reef aquarium, it is quite important to avoid introducing them into the aquarium.

Lastly, we should ensure that our clam has a healthy byssal organ. The byssal organ is not vital for most clams — after a certain point in their development it is not needed anymore and the clams spontaneously throw it off. But when clams are prepared for shipping, the byssal organ is sometimes torn from its attachment site. If this damages the sensitive muscular attachment of the byssal organ inside the clam (Knop 1996), it will cause grave injury to the clam. Not all of these clams will necessarily die, but many of them may suffer from infections at the site of the injury (Sprung and Delbeek 1994). If the clam is holding tight on a rock substrate, we can be assured that its byssal attachment is not injured.

[damien]

want to add,

healthy clams must have full mantle extensions.

[chinmo]

Cool info!

[Dispar_Anthias]

Tridacnid clams — and clams in general — have a much more complex physiology than corals. Their ability to regenerate damaged tissues or organ systems is much more limited, and, unlike a soft coral, a clam often cannot recover from damage caused by unsuitable environmental conditions.

So, we must use caution when choosing a clam from an aquarium store. Here are a few hints that will help you in making sure that a clam is healthy and has been kept under suitable conditions. More detailed information about this important topic can be found in the chapters “Buying Clams in the Pet Shop” and “Clam Diseases” in my book Giant Clams (Knop 1996).

If you are interested in a particular clam and plan to purchase it, you should first look at the stocking conditions of the store in general. Is the lighting sufficient and of the right spectral composition? Even a few days with unsuitable lighting will stress the clam’s adaptation mechanisms. Is the water quality sufficient? Is there foam fractionation? Next, look for empty pairs of shells in the tank. If there are a lot of them in the stocking tank, in neighboring tanks, in a sump or any other place in the store, while this does not necessarily say anything about the health of the clam we have chosen, it might give us an indication about this particular store’s success in keeping tridacnid clams, as well as the condition of the recent clam shipment that included the clam we have chosen. Many retailers import clams directly, and if a clam shipment arrives in bad condition there are often lots of empty shells.

If the clam has been imported very recently (a few days before) you should wait a few more days before purchasing it. During the first two weeks after shipping, clams are still undergoing an adaptation period, adjusting to their new environment. If possible, the clam should not be placed in yet another new tank environment during this period.

The most visible indication of the health of a tridacnid clam is the incurrent syphon. This slit-shaped opening should be closed most of the time. Normally, clams open it just for a short period of time. If the incurrent syphon is wide open or “gaping” (Sprung and Delbeek 1994), the clam is probably in a weakened state, caused most likely by the stress of shipping. This condition sometimes disappears after a few days, but the percentage of losses is quite high among these “gaping” clams, so they are best avoided.

Another obvious sign of health in tridacnid clams is the reaction of the clam to being shaded. If we block the illumination by holding a hand between the light and the clam, the syphonal mantle should partially retract spontaneously. This is a natural protective mechanism — if the clam is in a weakened state, it might occur slowly or not at all.

If the clam of your choice has a good reaction to having its light blocked, and the incurrent syphon is not “gaping,” the next thing to look for is bleaching or fading spots on the syphonal mantle and parasites/predators on the shells. The most common predators on tridacnid clams are the pyramidellid snails. These tiny, white-shelled snails sometimes spend the daytime on the upper shell margin of the clam, but mostly they hide on the bottom of the shell during the day. At night they travel up to the syphonal mantle and suck the blood with the help of their tussel (Knop 1996). Because they readily propagate in a reef aquarium, it is quite important to avoid introducing them into the aquarium.

Lastly, we should ensure that our clam has a healthy byssal organ. The byssal organ is not vital for most clams — after a certain point in their development it is not needed anymore and the clams spontaneously throw it off. But when clams are prepared for shipping, the byssal organ is sometimes torn from its attachment site. If this damages the sensitive muscular attachment of the byssal organ inside the clam (Knop 1996), it will cause grave injury to the clam. Not all of these clams will necessarily die, but many of them may suffer from infections at the site of the injury (Sprung and Delbeek 1994). If the clam is holding tight on a rock substrate, we can be assured that its byssal attachment is not injured.

cool info... that why now i dip all my clams be4 going into the tank

[sherman]

Dip in what?

Regards

Sherman

[Dispar_Anthias]

Dip in what?

Regards

Sherman

RO/DI fresh water

Oh ya... my experience recently... I got a squamosa clam.... this time instinct and experience tells me to dip the clam and not try my luck.... so i dip it and guess what i found... 2 pyramid snails pop out....

[scarab]

RO/DI fresh water

Oh ya... my experience recently... I got a squamosa clam.... this time instinct and experience tells me to dip the clam and not try my luck.... so i dip it and guess what i found... 2 pyramid snails pop out....

Bro, dip for how long ah?

[Dispar_Anthias]

Bro, dip for how long ah?

RC/ US reefers dip their clam for ard 20mins but I usually dip for ard 5-10mins....

[chinmo]

RC/ US reefers dip their clam for ard 20mins but I usually dip for ard 5-10mins....

bro DA, any way to tell if the clams is infected by the snails?

[Dispar_Anthias]

bro DA, any way to tell if the clams is infected by the snails?

look at every scales of the clam shell for tiny white snail... and also the base of the clam... thats where they usually hide

[happy]

Just one more question, do we need to boost up the pH value of the freshwater before dipping the clam?

[Lester]

hi

will the clam die if dip in freshwater ???