A few questions regarding clams...


Ultimate Reefer
Do clams close up fully when its dark?

If not then roughly how much do they stay open?

How can one tell if a clam is needing more light?

What charecteristics lets us know that a clam is happy/ie tank conditions are fine for it?

These may be silly questions, but they are questions that the various articles dont answer and I am curious. I think knowing the answers can be helpful to all newbies and even possibly the more experianced hobbyists. Thanks.
I have a derasa now. Small, perhaps 2.5" long. Closes up completely at night.

Had a beautiful 4" Squamosa. Didn't close up at night, though it did pull the mantle in a bit.

When the squamosa, if it was stressed, the mouth would open very wide, you could see all the insides very easily. That's stress. In addition, the exit valve should be spouted up, like a min-volcano. If it's restracted it's not happy.

As far as happy, I never did find that part out. What kind of clam and how much light are you predicting?

I saw 2" mantle extension on my Squamy during the day (29 reef, 220 watts PC lights) and on my Derasa (which is smaller) 1" with same lights (in a 5.5 nano)

A happy/healthy clam should respond quickly to shadows or hands in the tank/changes to the surroundings. Turn off one light and watch the clam close rapidly. To me that says it's in good shape. Limp clams are not healthy clams.
AttackDonut: What happened to the squamosa clam? Did you sell it or did it die?

I bought a Deresa clam to keep in my aquamedic tank. The tank area is 45G and the depth is 18iches from sand to water surface. The Derasa clam is on the sand bed directly under the lights.

Lighting is a combo of 150w MH (10K Ushio) Aquaspacelight and 2x39w of HO T5 (9.5K and Actinic).

The lights site 3.5 inches above the surface of the water.

The clam is about 3.75 inches.

I am not exactly sure how a clam behave etc so thats why I am asking those questions.

Do you think my lighting is enough?

What about a Maxima placed in the top half of the tank?

Here is a pic of the clam a day after its been in the tank:


Note the shady area on the left is due to an urchin sitting just above the clam on a rock.

The clam was placed a little to the right but it moved closer to the rock.

Thanks for the help.
I've only had my clams for about a week (3"maxima and a 4"squamosa)but I'll share anyway.

At night they pull their mantles in but they don't really close up. My squamosa is in my 55 on the sandbed and looks perfectly fine. He hasn't moved except he's kind of sunk in the sand a little I'm gonna bury a flat rock under him for him to attach to. My max is in my nano and has jumped off of the rocks like three times. Every time was at night. The spot he is currently in he has attached on a flat rock and I'm hoping he's gonna stay there. I'm trying to keep my hands out of the tank as much as possible, but I really don't want him to attach to any spot that I can't see.

As far as being happy or needing more light, I'm gonna assume that if they needed more light they would slowly start to diminish. IE bleaching, not opening. But some threads have referenced them dying all of a sudden, so I guess it's hit or miss.

I read the new Calfo/Fenner "Reef Invertebrates" book and it has a section on tridacnids which is pretty good, I'm going to buy Knop's "Giant Clams" book but my LFS wants $69.99 for it. So I'm gonna just order it.