Tridacnid Clams

The giant (Tridacnid) clams commonly found in our hobby are Crocea, Derasa, Maxima, Gigas and Squasmosa. In general they are hardy animals but require intense lighting and stable water parameters. It's important that temperature, pH and salinity is not constantly swinging. Nitrates (under 10) and phosphates are less of a concern but calcium (350mg/L or more) and alkalinity (8-12 dKH) are very important for long term success.

Lighting:

As a rule of thumb, the brighter the clam the more light it will require. Crocea and blue Maxima clams require the most light of all the clams and require metal halides or powerful T5 lighting. There is no general formula on how much light you need as it depends on too many variables such as the type of clam, depth of placement and tank size. However, It's best to use a light spectrum of around 10k to 14k.

Acclimation:

Like most inverts, acclimation is very crucial to survival. Acclimation time can range from 1 to 3 hours and the best way to do this is to use drip acclimation. If you don't feel like testing the parameters in the bag and comparing them to your own tank, it's best to play it safe and acclimate for 2-3 hours. This method can be found here.

It's generally recommended that you also do a light acclimation by placing the clam low in the tank and slowly move it up towards the light. If you decide to do this, make sure to place a piece of flat rubble under the clam so that it will not have to reattach when it moves up.

Flow:

In general clams don't enjoy direct flow but the tank itself should have moderate to high flow. Make sure the clam mantle is not flapping around. Slight mantle movement is fine.

Feeding:

Clams less than 2 inches require feeding. Live phytoplankton is probably the best choice. Another good option is oyster eggs. Never feed clams large particles of foods such as Mysis, Brine or any type of shrimp, and never target feed. If its individual particles are visible then it's probably too big. Clams that are around 3 inches or larger can rely 100% on photosynthesis and will not demand feeding but can benefit from them.

Healthy Clams:

There are various ways to check if clams are healthy.

1. Do a shadow test: Healthy clams are extremely sensitive to shadows and when you wave your hand over a clam it should retract quickly. When we take a top down photographs it's always a major pain since we are directly over the light.



Here is a video of how fast clams should respond to light.

2. Touch test: The slightest touch should cause the retraction of the clam's mantle. Sometimes running across the room can cause the mantle to retract!


3. Check for gaping. Healthy clams should not have large circular holes at their mouth (intake). There is an exception with Crocea clams which can gap when it's perfectly healthy. However, if you do see your Crocea gap you should be on the look out to see if it's shells are gaping. You can tell by looking at the side of the clam where the two shells are joined and make sure it's not gaping too much.



4. Check for parasites on their shell. The most common parasite is the pyramid snail which resembles a small grain of rice. They usually come out to prey at night so check after a few hours the lights are off.
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Colossi