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Urchinhead

A FAQ on Clams

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Because this seems to come up time and time again here and because I had many questions that had contradicting answers about having a clam in a nano sized tank under less then metal halide lighting I did quite a bit of research on the subject and have consolidated it into a FAQ.

 

Clams

 

Scientific Information:

 

Phylum: Mollusca

Class: Bivalvia

Order: Veneroida

Family: Tridacnidae

Genus: Tridacna

Species: Multiple. See below

 

 

Common Names:

Crocea, Derasa, Gigas, Maxima, Squamosa, giant clam, fluted clam

 

Origin:

Indo-Pacific

 

Introduction:

This article is divided into 2 sections. General Information and clam specific information based on species. General Information contains general notes on husbandry, disease, and predation while species specific sections deal with specific clam species broken out by type of clam and contains specific details on tank size, diet requirements, special needs, and the like.

 

General Information:

There are five species of clam commonly found in the aquarium trade and they are some of the most beautiful non-fish species one can have in a tank. They also have a reputation of being very fragile, difficult to keep, require expensive equipment/lighting, and great attention to detail on the status of the tank so keeping one should be attempted by only experienced reef/salt water tank hobbyists with Metal Halide lighting and constantly monitored and controlled tank parameters. This common belief is based more on word of mouth and urban myth than actual empirical evidence and as such should be discarded by the salt water enthusiast wanting to attempt a clam in their tank.

 

Clams are colorful, interesting, and beneficial additions to a stable and mature tank. I say beneficial because they are a source of nitrate and phosphate uptake[1] which means that they will help to keep your tank environment clear of these unwanted contaminants and assist in control of nuisance algae and tank stability.

 

Please note that while clams will help in the control and export of nitrate and phosphate they should not be placed in tanks with high levels of either and should not be used as a primary form of export of these contaminants as the total uptake per clam is not sufficient to deal with a high level of either and high levels of either will hurt and possibly kill the clam. Something more suited to the task such as water changes and/or macro algae such as Chaetomorpha should be used.

 

It should be noted that as with all marine animals and corals each particular individual will vary in terms of hardiness and ease of care but as a whole the various species of clam can be a very welcome and interesting addition to a nano aquarium with the understanding that when selecting a clam species the tank environment where the clam will be placed must be capable of supporting said species of clam and that there is more to keeping a clam healthy and happy than just dropping it in the tank and hoping for the best.

 

While clams, like some corals, primarily rely on symbiotic zooxanthellae colonies for nutrient generation and thus are considered photosynthetic feeders (more on this below) the actual coloration of a clam's mantle doesn't come from the zooxanthellae itself. It comes from cells called iridophores that contain color pigments. These pigments are mainly in the color range of blue to brown or green to yellow and the pigments' purpose is to protect the clam against excessive light and UV radiation.[1]

 

Clams should be placed in tanks that are over six months old and are stable. The reason behind this is that, like most all invertebrates, they do not tolerate rapid and/or large changes in various parameters such as salinity and ammonia/nitrate/nitrite/etc and a tank is still considered to be going through its initial cycling period and not truly 'stable' until about the 6 month mark.

 

Clams can close their shells with enough force to expel a large volume of water. Clams placed near the top of the tank can squirt with enough force to strike the lighting system or areas surrounding the tank.

 

Clam's can also accidentally trap fish. Fish that perch such as watchman gobies or hawkfish can become trapped as can overly curious fish that explore the clam or swim too closely. This situation is usually fatal for either the clam or the fish. The more the fish struggles the more the clam will close and stay closed meaning that the clam must be manually pried open most likely killing the clam or the fish dies at some rate depending on the part of the fish captured.

 

Clams should be placed on as flat a surface as possible with the byssal opening (bottom of the shell) facing down and the mantle facing as directly up as possible. Do not place the clam between large rocks, inside small holes, or against a wall as it may prevent it from opening fully.

 

A clam may also fall over several times before it attaches. Small rocks can be placed around the clam to help it stay upright but care should be taken to make sure that the rocks are not limiting the clam's ability to open. Repeated falls or prolonged lack of attachment can be indicative of an unhappy clam usually due to suboptimal lighting and/or too high a water flow and thus the clam should be repositioned.

 

Clams are susceptible to stings from aggressive corals and anemone so care should be taken to ensure that the clam is not within stinging range of either.

 

Crocea and Maxima species of clam are found in rocky habitats in the wild and have very fine gills so it is best to place them on rocks or if in the sand bed on top of a small rock that sticks out slightly which will allow them to attach firmly to something and keep any fine sand from entering their gills. Squamosa, Derasa, and Giga's are best placed on sandy substrates with a rock underneath them as they will burrow down in the sand bed and attach themselves to the bottom of the tank.

 

Clams will attach themselves to the substrate or rock via their byssal gland aka foot. Once attached care should be taken in attempting to move a clam and if the clam comes already attached to something it is best to leave it attached and glue or place securely that object to the spot in the tank where the clam is to be placed.

 

The best species of clam for Nano tanks are the Crocea, Squamosa, and Maxima. Crocea can be kept in the smaller nano tanks, under 20 gallon, as they will reach a maximum size of about six inches while the Squamosa and Maxima's can reach sixteen inches when fully grown and as such thought should be given to what to do with the clam when it gets too big for the tank. It is important to note that keeping a clam in a smaller tank is more difficult than a larger tank, over 29 gallons, due to the feeding and water quality requirements of the clam.

 

Lighting:

The short answer to the question of what lighting is required for clams comes down to: It depends...

 

The long answer is that after an exhaustive search for empirical studies on the lighting requirements of clams kept in the amateur/hobbyist aquarium no actual studies have been published at time of writing of this article. It is rumored that James Fatheree has a study of clam species under PC, T5, and MH lighting but at time of writing of this article there is no information in the public domain on this study.

 

The common wisdom by experts in the field of aquarium husbandry[1], review of hobbyist articles[2][4] and deductions based on scientific articles on commercial clam husbandry[3] is that the higher the light level the better for the clam depending on the species of clam.

 

This means that it is possible to keep a healthy clam under PC lighting just as it is possible to kill a clam kept under Metal Halide lighting depending on the species of clam and the individual clam itself.

 

In general a minimum of T5 is best for the clams that will be comfortable in a nano tank with MH being optimal and PC possible with lower light requirement clams. The key being the lower the lighting the closer to the light the clam must be placed. So with PC lighting the clam should be near the top 10-15% of the tank or in a shallow depth tank. With T5 and depending on the species of clam and depth of the tank the upper third of the tank is best. With MH and again depending on the species of clam the clam should be in the lower third of the tank.

 

 

Water Parameters:

Previously the common wisdom was that clams obtain all of their nutritional requirements from the symbiotic zooxanthellae they host thus the need for high lighting. This has been found to be incorrect.[1] Clams under 3" in size rely primarily on filter feeding to sustain growth and clams over 3" still engage in filter feeding for actual nutrient intake as well as for key elements such as calcium and some nitrates, phosphate, and the like. More on key elements below. Thus water parameters are important to proper clam husbandry.

 

Proper water flow is important to clams because of their filter feeding. They need enough flow to strain water through them for food but too much flow will cause the water to pass too quickly through them to properly filter out the needed nutrients and will irritate the clam causing it to close up. So they should be in a relatively moderate flow area of the tank and not directly in the path of a power head's stream. As a rule of thumb use the same flow requirements for moderate flow corals as you would a clam. A good indication of too much flow would be either the clam constantly retracting its mantle or the mantel blowing around.

 

Tank temperature should be kept as stable as possible and in the range of 76-82 degrees F.

 

PH should be as stable as possible and range between 8.2 and 8.4

 

Salinity should be as stable as possible and range between 1.022 and 1.026.

 

Key elements that clams need for proper growth include calcium and to a much lesser extent nitrate, phosphate, etc. Calcium is the key element for a clam and should be maintained at the same levels required for corals, 400-450 ppm.

 

 

Predators:

Clams are not recommended in a tank that contains any of the following:

 

Fish:

Angels

Some wrasses

Butterfly's

Triggers

Puffers

Tangs

Some blennies

 

All of these type of fish will nip at a clam's mantle.

 

Parasites:

Pyramidellidae (rice) snails

Vermetidae snails

Bristle worms

Fire worms

 

Invertebrates:

Most larger crabs

Lobsters

 

Crabs and lobsters as well as some shrimp are opportunistic predators and have been known to go after clams once they realize that a relatively easy and stationary food source is available.

 

Feeding:

As noted above clams are primarily photosynthetic but do benefit from supplemental feeding. As they are filter feeders they will benefit from the same foods fed to most corals including:

 

phytoplankton

zooplankton

oyster eggs

 

It is possible to target feed but in general the same system used for feeding corals should be used for feeding clams. Turning off the power heads and filter system for 30-60 minutes followed by pouring of the food source into the water column will allow the clam to filter feed.

 

Acclimation Process:

Gradual. An example acclimation method would be to place the clam in a bucket or container with the water it came with, a heater, and a very small power head. Over a 30 to 40 minute period remove 4 oz of old water and replace it with 4 oz of water from your tank repeating every 7-10 minutes for about 30-40 minutes. (Note this assumes you have more than 12 oz of original water and that the original water is not fouled or contaminated. Drip method would be best if you do not have at least 12 oz of original water)

 

It is also important to 'burp' a clam.[2] When moving a clam from one location to another where the clam is out of the water it is possible for the clam to develop a potential air embolism due to some air being drawn into the gills of the clam. When the transfer is complete gently rotate the clam 360' several times to release any trapped air bubbles.

 

Things to watch out for:

As with all invertebrates copper based medications are fatal to clams.

 

Clams are sensitive to rapid shifts in salinity, temperature, and PH which can be fatal.

 

A good indication of a healthy clam is does it react quickly to stimuli such as a shadow passing over it? If the clam rapidly closes itself then reopens itself after you pass your hand over it to cause a shadow or a fish swims over it then your clam is most likely healthy.

 

Clams have a byssal gland, also known as a foot, which they use to attach themselves to substrate or rocks. Care should be taken when dealing with a clams byssal gland when moving the clam. Damage to the byssal gland is usually fatal. If the clam needs to be moved lift the shell gently and with a sharp knife cut the byssal threads as close to the substrate as possible

 

Pinched/Ruffled Mantle:

The mantle will curl in and up fashion and continues in this state until the clam expires. Per clamsdirect.com it is believed that pinched mantle is caused by an unidentified protozoan and the treatment recommended is a fresh water dip in PH/Temp adjusted RO water for 25 minutes. After dip the clam should be gently shaken to remove the RO water and then placed into a Hospital tank if possible.

 

The possible use of a UV Sterilizer should be considered for use on the main tank in order to eliminate any free floating organisms. While this is not specifically discussed on clamsdirect.com logic dictates that the use of UV light to kill said free floating organisms is successful in other types of like diseases and parasites thus it may be appropriate for clams as well.

 

Gaping:

Clams have an intake siphon and an output siphon. The intake siphon looks somewhat like a mouth and is a slit opening that is found on the center line off to one side of the mantle while the output siphon looks like a cone or rod. A clam is considered to be gaping when the intake siphon is open very wide almost like a tear. Indication of gaping vs. normal feeding would be not only that the intake siphon is open abnormally wide but that the mantle isn't extending normally and the shell is fully open. Gaping is caused by poor lighting, parasites, or poor health and if gaping continues the clam will not recover. Treatment should be examination for parasites followed by moving the clam to a higher or lower level in the tank depending on its proximity to the light source.

 

Bleaching:

Bleaching is exhibited as spots or areas of discoloration (white) on parts of the mantle and is usually caused by suboptimal lighting but can also be caused by parasites. Treatment should be to first examine shell for boring worms or sponges, snails, and the like then treat for poor lighting.

 

Clam Species:

 

Common Name: Crocea

Scientific Name: Tridacna Crocea

Max size: 6 Inches

Tank size: Possible in tanks under 20 gallons

Recommended in tanks >30 gallons

Food: Photosynthetic but benefits from

zoo & phyto plankton

Reef safe: Yes

Lighting Req: High. T5 or above

Placement: On rocks

Notes:

Should be placed middle to high up in the rock work depending on the color intensity of the mantle. Blue requires more light than green or brown. Prefers moderate flow and will attach firmly to rock. Easy to care for and moderately hardy but does require more light than bottom dwellers. Possible to keep under PC lighting but strongly not recommended. Purchase clams over 2" in size as smaller has a high mortality rate. Will reach maximum size in 5-7 years.

 

Common Name: Maxima

Scientific Name: Tridacna Maxima

Max size: 6 Inches

Tank size: Possible in tanks under 30 gallons

Recommended in tanks >30 gallons

Food: Photosynthetic but benefits from

zoo & phyto plankton

Reef safe: Yes

Lighting Req: High. T5 or above

Placement: On rocks

Notes:

Should be placed middle to high up in the rock work depending on color intensity of mantle. Blue requires more light than green or brown. Largest color spectrum of all clams. Needs supplemental feeding for proper growth. Prefers moderate flow and will attach firmly to rock. Can be difficult to keep and is less hardy than other clam spcies. Tank size above 50 gallons is recommended due to potential size. Will reach maximum size in 5-7 years. Purchase clams over 2" in size as smaller has a high mortality rate.

 

Common Name: Derasa

Scientific Name: Tridacna Derasa

Max size: 18 Inches

Tank size: Possible in tanks under 50 gallons

Recommended in tanks >50 gallons

Food: Photosynthetic but benefits from

zoo & phyto plankton

Reef safe: Yes

Lighting Req: Moderate. PC or above

Placement: Low in tank but on rock

Notes:

Should be placed low in the tank but not directly on sand bed as clam will blow away sand and attach to glass on bottom. If under PC lighting higher up in the tank is required. If under T5 or above they can be placed on the sand bed but should have a rock buried under them to attach to. Prefers moderate flow and will attach firmly to rock. Is hardy and more low light tolerant than Maxima or Crocea. Tank size above 50 gallons is recommended due to potential size. Will reach maximum size in 5-7 years. Purchase clams over 4" in size as smaller has a high mortality rate and require manual feeding of phytoplankton.

 

Common Name: Squamosa

Scientific Name: Tridacna Squamosa

Max size: 16 Inches

Tank size: Possible in tanks under 50 gallons

Recommended in tanks >50 gallons

Food: Photosynthetic but benefits from

zoo & phyto plankton

Reef safe: Yes

Lighting Req: Moderate. PC or above

Placement: Low in tank but on rock

Notes:

Should be placed low in the tank but not directly on sand bed as clam will blow away sand and attach to glass on bottom. If under PC lighting higher up in the tank is required. If under T5 or above they can be placed on the sand bed but should have a rock buried under them to attach to. Prefers moderate flow and will attach firmly to rock. Is hardy and more low light tolerant than Maxima or Crocea. Tank size above 50 gallons is recommended due to potential size. Will reach maximum size in 5-7 years. Purchase clams over 4" in size as smaller has a high mortality rate and require manual feeding of phytoplankton. Leave plenty of room around clam for growth.

 

Common Name: Giga

Scientific Name: Tridacna Giga

Max size: 52 Inches (4.25 Feet)

Tank size: Possible in tanks under 100 gallons

Recommended in tanks >100 gallons

Food: Photosynthetic but benefits from

zoo & phyto plankton

Reef safe: Yes

Lighting Req: Moderate. PC or above

Placement: Low in tank but on rock

Notes:

Should be placed low in the tank but not directly on sand bed as clam will blow away sand and attach to glass on bottom. If under PC lighting higher up in the tank is required. If under T5 or above they can be placed on the sand bed but should have a rock buried under them to attach to. Prefers moderate flow and will attach firmly to rock. Is hardy and more low light tolerant than Maxima or Crocea. Purchase clams over 4" in size as smaller has a high mortality rate and require manual feeding of phytoplankton. Leave plenty of room around clam for growth. This clam is NOT recommended for any tank under 100 gallons as it can grow to 4.25 feet and weigh over 500 lbs.

 

 

References:

[1] Ronald L. Shimek, PhD; James W. Fatherree, MS; Robert Fenner, MS

[2] http://www.clamsdirect.com/forum/index.php

[3] www.ctsa.org/upload/publication/ CTSA_143631672855187292852.pdf

[4] http://www.wetwebmedia.com/tridacsysfaqs.htm

Edited by Urchinhead
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good info,but ezcompany had a thread like this.

 

Yes. I know. But it wasn't complete and consolidated or categorized. What's your point?

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phil121   

Great article! I am hoping to get a clam soon and this is a very useful write up. Thanks.

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divecj5   

Great article....thanks for putting the time in to write this. Very well done and nicely categorized.

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This is a very helpful thread, why aren't EZ's and/or Urchins thread stickied at the top. The only thing i want to know this article hasn't told me is how demanding the nutrient requirements are, meaning how fast can they strip the water of calcium?

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Rocket   

Excellent read! Helps in making the choice between maxima and crocea.

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Do maximas really get to 16"? I've been eyeing some gold teardrops that the LFS has had for like a year. They are about 8" I think, and he says they have been slowing down their growth.

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Do maximas really get to 16"? I've been eyeing some gold teardrops that the LFS has had for like a year. They are about 8" I think, and he says they have been slowing down their growth.

 

If it said 16" for a maxima my apologies. It should be 6".

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willyboy   
If it said 16" for a maxima my apologies. It should be 6".

 

well could you change it cause it kinda threw me off. thanks

 

It will also help others

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andre   

might want to add lawnmower blenny to the list of fish that nip on clams. mine nipped the sh** out of my derasa.

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well could you change it cause it kinda threw me off. thanks

 

It will also help others

 

Done.

 

thanks for the great info

 

You're welcome.

 

 

might want to add lawnmower blenny to the list of fish that nip on clams. mine nipped the sh** out of my derasa.

 

Done.

 

might want to add lawnmower blenny to the list of fish that nip on clams. mine nipped the sh** out of my derasa.

 

Done.

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spanko   

Nice job UH!!

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So croceas and maximas are smallest ?

 

Yes. With Crocea's being the most sensitive to light requirements and needing the most care of the two.

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I wish all noobs would read this. Seems to be alot add crocea to tanks with pc lighting.

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