Besides the usual community fish species, shrimp, snails, and crayfish kept in the home aquaria, are you aware that aquatic animals such as Freshwater clams and mussels are equally good and interesting additions to well-established freshwater tanks?
Well, Freshwater clams are not that popular in the aquarium hobby, yet a good number of aquarists have these small bivalves in their aquariums— and they do a decent job at filtering particulate matter, suspended algae, and detritus from the tank; these things serve as a major dietary requirement for their sustenance.
Freshwater clams are rated on the easy-medium care level because they have specific requirements for the tank set up to thrive. Despite being hardy species, they are quite particular about certain needs like cool water temperature, ample water movement, fine substrate, supplemental feeding, calcium addition, and peaceful tank mates.
Keep reading for more information about these amazing pet bivalves and how to care for them in your home aquarium.
|Important: NEVER release Freshwater clams into the wild. Among freshwater animals, Corbicula fluminea has become one of the most successful invasive species all over the world. It is listed among the ‘‘worst invaders’’ within Europe.|
Quick Notes about Freshwater Clams
|Common names||Freshwater mussels, Basket clams, Asian clams, or Asiatic clams|
|Scientific name||Corbicula spp.|
|Tank size (minimum)||10-gallons (~40 liters)|
|Size||up to 2 – 3 inches (~5 – 7.5 cm)|
|Optimal Temperature||65 – 80 °F (18 – 26 C)|
|Optimal PH||7.0 – 8.0|
|Optimal GH||5 – 20|
|Nitrate||Less than 20 ppm|
|Diet||Algae eater/omnivore (filter-feeding)|
|Temperament||Peaceful and solitary|
|Life span||1 – 2 years|
|Color Form||Golden tan, light or dark brown|
Origin of Freshwater Clams
Freshwater clams are aquatic bivalve mollusks in the order Venerida. This order comprises mostly saltwater and a few freshwater bivalve mollusks, it is further subdivided into several families of saltwater and freshwater clams which includes the popular freshwater clam family Corbiculidae, also known Cyrenidae.
Corbiculidae is a small family of clams, commonly known as basket clams owing to its concentric-ribbed shells, the name Corbiculidae stems from corbis — Amharic word for “basket”.
This family houses the widely known freshwater clam genus Corbicula. Going further, Corbicula is a genus of freshwater and brackish water clam species that are native to East Asia.
Species like Corbicula fluminalis and Corbicula fluminea are famous due to their widespread usage in aquariums. Both species are indigenous to Asia, and that’s why they are collectively regarded as “Asian or Asiatic clams” in the aquarium hobby.
In Southeast Asia, these species are known as the golden clam, prosperity clam, pygmy clam, or good luck clam.
Habitat of Freshwater Clams
The species of Corbicula are native to East Asia, and they occur in freshwater environments (rivers, streams, and lakes) in China, Japan, Taiwan, the Philippines, and parts of South Korea.
Also, as an introduced/invasive species, they are present in regions like South America, North America, West and East Europe, and North Africa. Basically, Freshwater clams can be found on every continent except for Antarctica.
Description of Freshwater Clams
Freshwater clams of the family Corbiculidae are usually golden tan, light or dark brown in color, sometimes with irregular white streaks.
Their overall body comprises a shell measuring about 2 – 3 inches (5 – 7 cm) in size.
This calcareous shell is divided into two valves, commonly of equal size, held together at the hinge by a ligament which also allows it to open. The shell is equally capable of closing tightly through the contraction of two adductor muscles found at the inner surface of both valves.
The invertebrate possesses a powerful, muscular burrowing foot and this allows it to bury itself into the substrate for extended periods.
Also found within the bivalved shell is a soft tissue, typically off-white or slightly pink, and siphons responsible for water passage, respiration, and suspension-feeding.
Depending on the species, the lifespan of Freshwater clams ranges between 1 and 5 years in a variety of ecosystems.
Difference between Corbicula Fluminea and Corbicula Fluminalis
The taxonomy on species level is very difficult. Currently, there are more than 460 Freshwater clam species!
Even the most aquarium common species like Corbicula fluminea and Corbicula fluminalis are often confused for one another. However, it’s possible to tell both species apart by the number of ribs on the shells:
- Corbicula fluminea has 7-14 ribs per centimeter (3/8 Inches) while the latter bears 13-28 ribs.
Another clear distinction is the shape:
- Corbicula fluminalis is said to be rounder whereas Corbicula fluminea has a slightly flatter shape.
Behavior of Freshwater Clams
Freshwater clams are peaceful and solitary, and they will not harm your aquarium fish and invertebrates.
Clams habitually embed themselves, partially or completely, into the fine substrate (sand); spending a huge chunk of their time immersed in the deep bed. Other times, they would move briefly around the tank or just sit and relax comfortably on top of the substrate.
Furthermore, they tend to filter large amounts of aquarium water to feed and breathe. Freshwater clams have the tendency to promote clarity of the water by filter-feeding on particulate matter and phytoplankton; there are several cases of clams clearing green water in the aquarium within short periods.
Freshwater clams do not exhibit a fast growth rate. However, if they are healthy and well-fed, then you should notice a slow but steady growth.
- Social: No
- Active: No
- Peaceful: Yes
- Burrowers: Yes
Feeding Freshwater Clams
Their main diet consists of particulate matter and suspended microalgae which they filter out from the water column using their paired siphons. As water passes along the gills, organic materials become attached to a mucus lining and are transported to the stomach.
Freshwater clams do not like tanks that are “too clean”. It is absolutely important that aquarium water needs to have plenty of very tiny debris, detritus, and decaying matter floating in it.
In addition to their filter-feeding abilities, they can also conduct pedal feeding by feeding on organic matter or detritus available on the bottom of the aquarium. However, it is no their favorite way of feeding. So, if Freshwater clams are doing this regularly, it is a sign that there is not enough current or food in the current, and this should be resolved.
Other than that, Freshwater clams will readily accept powdered food items like (links to Amazon):
- spirulina powder,
- Golden Pearls in the 5-50 micron size,
- powdered rotifers, etc.
In case of emergency, you can finely crush food items like flakes, pellets, and algae wafers.
To keep your Freshwater clams healthy and active, make sure you feed them 2 – 3 times a week. Moreover, if you notice that your clams are no longer accepting meals, check to see if they are been threatened by a curious or nippy tankmate because they won’t feed when agitated.
|Don’t forget to offer them calcium supplements as it helps strengthen their calcareous shells. Therefore, I highly recommend reading my article “How to Supplement Shrimp and Snails with Calcium”.|
- Diet Type: Omnivore
- Food Preference: Algae
- Feeding Frequency: Daily
Are Freshwater Clams Plant Safe?
They will not eat any healthy plant in the tank. They simply do not eat healthy, living plant material.
However, the burrowing activity of Freshwater clams can displace some of your plants in the tank. Therefore, floating plants, plants that do not require substrate (like Anubias, Java fern, Java moss, Marimo Moss Balls, Subwassertang, etc.), or fake plants are the best choice.
Tank Requirements and Water Parameters
As with any fish, shrimp, or snail tank, make sure that the tank is set up correctly, and that the water is properly cycled.
You can house the Freshwater clam in a tank of at least 10 gallons (~40 Liters). Anything smaller and you will have problems due to their unique feeding behavior.
Bear in mind that having larger tanks will help promote the stability of the water chemistry. In addition, it allows you to stock multiple clams at a time. Therefore, opt for tanks with more than 20 gallons (80 liters) to enjoy the outlined benefits.
Water type, Temperature, Hardness, and pH:
Temperature: The ideal temperature for keeping Freshwater clams is between the range of 65 – 80 °F (18 – 26 C). They have a soft spot for cooler temperatures, so you should aim towards that. According to the study, their temperature tolerance has been widely perceived to be in the range of cold water 2 – 36 °C (35 – 96 F).
For example, they have a 75% survival when exposed to 0 °C (32 F) water for up to 4 weeks.
pH: Freshwater clams will thrive best in tanks with optimal pH values 7.0 – 8.0. Although they can tolerate pH 6.5 and lower, it is better not to leave them in acidic water for a long time (weeks). Acidic water slowly dissolves its shell! The harder water the better it will be for their shells.
Hardness: The ideal water hardness should be between 5 – 20 dKH to help them maintain a healthy shell.
Interesting fact: Corbicula species can live in fresh and brackish waters with salinity to 10–17 ppm.
They do not need high lighting; however, the lighting output should be bright enough to actively support the growth of their food – Green water algae. Obviously, you’ll have to remove any UV sterilization from the tank.
LED lighting or T5/T8 bulbs can be utilized for this purpose, also, ensure to supply at least 8 hours of lighting on a daily basis.
Since Freshwater clams love to burrow themselves into the substrate, the preferred substrate should be a fine one; of which sand is suitable.
Keep a minimum layer of 2 inches (5 cm) of fine sand on the bottom to allow the clams to burrow into whenever they desire.
Freshwater clams will appreciate a well-oxygenated tank with decent water flow.
Be sure to maintain moderate water flow in your tank to encourage the clams’ ability to filter huge amounts of particulate matter and planktons in the water column.
Low flow and low dissolved oxygen have been related with high mortalities in Freshwater clams.
The water currents in your tank should not be slow or too fast to avoid impeding on the organism’s feeding, if possible, place them in areas where the water is moving steadily.
Acclimation and Copper:
Like freshwater snails, clams are sensitive to copper (read my article about “How Copper Affects Dwarf Shrimp”). Watch out for signs of copper especially if you have tap water in your tank.
Do not forget that before adding them into the tank, it will be better to carefully acclimate them (read more about it here) as all invertebrates.
Basic Tank Equipment (links to check the price on Amazon)
Caring and Keeping Freshwater Clams
There are mixed reactions as regards the care difficulty of this aquatic bivalve mollusk.
Some aquarists are of the opinion that Freshwater clams are relatively easy to care for— if kept in a well-established tank with plenty of particulate matter, phytoplankton, and detritus to feed on.
Others do not share the same opinion as they view freshwater clam as a misfit considering how specific their demands. Situations such as lack of food, acclimation, or large swings in parameters can kill your Freshwater clam, thus releasing huge amounts of ammonia into the tank water.
So, there is the truth?
Actually, both sides are right.
They do not require a high level of care and attention to thrive in the aquarium when they have everything they need. Otherwise, it can go downhill very fast. Unfortunately, aquarists often treat them like snails – drop and forget. This is wrong!
Freshwater clam is an obligate filter-feeder. So, it needs a great deal of particulate matter, phytoplankton, and suspended detritus in the water column to consume regularly.
Endeavor to test the water regularly to keep the ammonia, nitrites, and nitrates levels in check. Also, be sure to carry out partial water changes of at least 20% every two weeks to maintain good water quality.
Since Freshwater clams are invertebrates, do not treat your tank with copper-based medications as it will lead to their demise. If you must, move your Freshwater clams to a separate tank and return them only when the copper present in the aquarium has been completely eliminated through chemical filtration.
In addition, proper acclimation is a must before adding these clams to ensure their survival.
Interesting fact: Corbicula species particularly tolerant to desiccation when low temperature and high humidity conditions coincide. However, according to the experiments, freshwater clams cannot tolerate desiccation under high temperatures. For example, a 100% mortality was recorded after 48 h (25 and 30°C or 77 – 86) for Corbicula fluminea, and an elevated mortality rate recorded after 24 h.
Checking and Handling Freshwater Clams
Furthermore, the clams need to be closely monitored from time to time— gently tap on the clam’s shell to be sure that they are still alive.
A healthy, live clam should respond to this nudge by moving or closing its shell hurriedly whereas a dead one won’t even respond at all. Make sure their shells aren’t too open. It is fine if they are slightly ajar but too wide is a sign of their death.
Note: Instead of assuming the worst immediately, you may want to take it out of the water to perform a simple smell test. A dead Freshwater clam smells awful (like rotten eggs), you will not confuse this scent with anything else.
In the event of death, quickly take the dead clam out of the tank to prevent it from decomposing and altering the water quality. A dead clam will cause ammonia spike that can ruin your tank, so take heed and always do the needful to keep it in the best health condition.
Reproduction of Freshwater Clams
Under optimal tank conditions, Freshwater clams of Corbicula species will breed in the aquarium.
Being self-fertile, simultaneous hermaphrodite, these clams are able to produce sperm which fertilizes the eggs internally.
Most larval development occurs in the gills and body cavity of adults. These features of the reproductive cycle, as well as early maturation (3–6 months), contribute to their successful invasion of new habitats.
When the fertilized eggs transform into larvae within the body of a mature clam. Corbicula species can broadcast spawn up to 570 mucoid larvae per day per individual, and more than 68,000 per year per individual
Sooner than later, they will metamorphose into juveniles and further into adult clams, and the cycle continues.
|Warning: Some clams reproduce by producing tiny microscopic larvae which attach to fish gills (potentially cause whirling disease which may even kill your fish) and drop off later on. Some clams can do this with any species of fish and some clams can only do it with certain species of fish. Therefore, DO NOT pick up freshwater species from your local pond or river! Their larvae can be parasitic. Choose livebearing clams only (like Corbicula fluminalis and Corbicula fluminea)!
In addition, when doing water changes, you should be very careful how you dispose of the water from the tank. If possible try not to dump water from your tanks into drains of any kind. They can be invasive species.
Freshwater Clams and Suitable Tank Mates
Freshwater clams are very peaceful and they will not cause any problems to their tank mates. They will be a great choice for any community tank.
Concerning the fish species and some natural enemies, freshwater clams should not be kept with Puffers, Cichlids, Loaches, and other aggressive fish.
Their tankmates should include other calm and peaceful community tank fish (for example, Panda Garra, Pygmy Cory Catfish, Otocinclus Catfish, etc).
Shrimp species that prefer slightly alkaline water will be the best choice to keep with White Wizard snails. For example, Vampire shrimp, Bamboo Shrimp, Amano Shrimp, Ghost shrimp, Cherry shrimp, Blue tiger shrimp, Snowball shrimp, Caridina cf. babaulti, Blue Velvet Shrimp, Malawa Shrimp, etc.
Freshwater clam’s tank mates can also include other snails like Black Devil Snails, Brotia Pagodula snails, Rabbit snails, Nerite Snails, Mystery Snails, Ramshorn snail, Malaysian Trumpet snails, and others of their kind.
Also, keep Freshwater clam away from all types of Crayfish (even Dwarf Mexican crayfish), most types of freshwater crabs, and even some types of predatory shrimp such as Macrobrachium family. All of them can be very aggressive towards the clams.
Buying Freshwater Clams
Freshwater clams are affordable, with the usual price ranging from $5 – $6 per clam at local fish stores and online stores. The average purchase size is typically ½ to 1” (1.5 – 2.5 cm) in diameter.
While shopping for this bivalve mollusk, seek for those with thick, ridged shells. In addition, the shells should be devoid of chips, cracks or holes, and the ideal color— golden tan, light brown, or dark brown. Quite often, the shells will possess white streaks or little green algae coats.
Bear in mind that healthy Freshwater clams will close their shells when poked to prevent damage to the slight white/pink inner tissue. Therefore, checking for some shell movements will increase your chances of selecting healthy specimens.
The freshwater clam may not the best pet invertebrate, yet it is a wonderful addition to mature freshwater aquaria as it adds a lot of diversity and helps keep the tank water clean and clear.
With the right care and maintenance practices, and optimal tank conditions, freshwater clams will thrive and live up to 2 years in the aquarium while bringing forth numerous offspring.