Who ate my clam?

[FrankM]

Hi, I have a 75 gallon reef tank. My 2 inch maxima clam, which I purchased a a few months ago and was doing fine, was eaten a few days ago. I am purplexed as to what ate it. I have a blue tang, yellow tang, a few anthias, a coral beauty angle, hermit crabs, an emerald crab, two fire shrimp, and two sand stars. Anyone with a clue since I would like to keep clams, if possible, but not sure of the culprit.

[Ninong]

Hi FrankM,


Maybe it had started to die and then the scavengers in the tank finished it off? Have you been feeding the tank live phytoplankton? Baby clams cannot survive on photosynthesis alone. A clam of that size gets about half of its energy from phytoplankton.

[FrankM]

I was feeding marine snow and other similar products every other day. Clam was open and full of color that day, never looked better. Tx for replying, I obviously don't want to add another clam until I figure out what happened.

[Ninong]

Mature clams get more than 90% of their nutrition from photosynthesis of the zooxanthellae in their mantles but young clams get only about 60% of their nutrition from this source. They must be fed regularly to survive. Marine Snow is 99% water according to independent analysis.

Clams feed on phytoplankton, preferably live phytoplankton of the appropriate size, shape and density. This is especially important for young clams.

[FrankM]

Thank you, this is very useful information.

[Clownfishcrazy1117]

Maybe the Angel?

[zhenya]

It's very hard to tell if the clam is doing bad, nutritionally speaking. Like Ninong had pointed out already, smaller clams won't survive on the photosyntesis alone and need to be fed live phytoplankton. Some aquarists, and even some vendors of clams, even go as far as taking clams out of the tank into the ball of water mixed with phytoplankton and let them feed there.
I was never a big fan of doing that, I think if you feed your tank with phytoplankton it should be sufficient. There are other critters in the tank that benefit from it as well...
Anyway, the clam may look 'gorgeously" colored and open up untill the moment it dies, then the clean up crew moves in overnight and finish the carcass off, hence why so often people are confused as to what happened (including me). I think we would be shooting in the dark at this time pointing the finger at any particular critter.

[Ninong]

I, too, have read that some hobbyists recommend removing juvenile clams from the tank and placing them in a bowl of tankwater that is green with live phytoplankton but I have also read that this is not a good idea for a couple of reasons. The most obvious reason is that the stress of frequently removing the clam from the tank offsets any possible benefits but another more pertinent issue is that the clam can't handle such a feeding overload.

Clams are designed to process only a certain amount of "food" at a time. They do it continuously. It must be "food" of the appropriate size, shape and density. If it isn't, it will be rejected. And if they are swamped with too much "food" all at once, the excess will be rejected. It is better to feed the entire tank smaller, but more frequent, amounts of live phytoplankton.

Another point is that if you're talking about either Tridacna crocea or T. maxima, both of those species should be allowed to attach to the substrate (rock). The only reason many hobbyists place these clams on the sand bed is so that they can view them easier. Crocea clams in particular should be high on the rock structure.

[Minh Nguyen]

Your clam should be growing. If you have a clam for several months, there should be new scutes and new white growth on the shell. If there is no growth, then the calm is not healthy and may be dying even if it is all open and show good color.
If clams doesn't get the required calories, it will use up it's reserve and died when this happen. I never intentionally feed my clams included Crocea that is about 1 inches and Maxima that is a little less than 1.5 inches. I think as long as you feed the tank well, and it there is plenty of light (at least 250 W MH for Crocea and Maxima under 1.5 feet of water, and everything else OK (Ca, alkalinity and low Phos), you clams should do OK.
How much light do you have on your tank?