How to tell gaping?


New member
Can someone tell me how to tell when a clam is "gaping" and possibly in trouble? I see my clam's "mouth" (whatever it is called, sorry) open different degrees all the time. Sometimes it is closed, other times it is fairly wide open, enough to see inside the clam. How do you know how much is too much? Is it ok, as long as the clam still reacts to stimul (closing when something moves over it)

Does anyone have pictures of normal opening vs gaping?

Is this gaping or normal?

Mind you I'm no expert

Mind you I'm no expert

Having just gotten my 1st clam, but that look sokay to me.

Mine *did* gap when I first got it, because I stupidly didn't acclimate it properly to my tank, so when I put it in, he opened his mouth so wide, it was almost spherical.

Since then he seems to have adapted (thank the gods) and is ok.

My guess is, if he opens and closes on a regular basis, he should be ok, only when he keeps his mouth open wide all the time would that indicate a problem.


I am not an expert, this is my uninformed opinion only, and I'm sure others here will give you better advice.
Now that is a good question. I haven't ever found anything about that in Daniel Knop's book but then again I might have missed it.

I have a T. Crocea that I have had in my holding tank for 3 weeks and would not ship as he was gaping more than I thought he should. Since then I have moved him to my display tank where he has attached to a LR and extends his mantle ever so nicely and retract to movement. That was 2 months ago and he still gaps.

After keeping Maxima's, Derasa's, Squamosa's and Crocea's is appears to more prevalent with Crocea's. Now I have a Squamosa that when the lights are out he gaps but when the light go on, after about a hours he closes.

Oh, the mouth as you say, is called in incurrent syphon. :)

I noticed today that the incurrent siphon :) was open, and shortly after I fed DTs to the tank, it closed and stayed closed for several hours after that.

I don't know if that is a coincidence, or part of the feeding process. Do they open the siphon more when they are hungry?
I have Daniel's Knop's Clam book if you want to borrow it. I was going to let you borrow it when you last came over. I forgot to ask if you wanted to borrow it then.
This is a good discussion and something I've been wondering about myself lately. What exactly is considered gaping and what is normal? The simple fact that the experts and the one good book on the subject don't spell it out leads me to believe it's not something that can be set in stone.

I have 4 maxima clams and they all seem to have their own kind of normal. My smallest, a 2-3" gold, seems to keep his incurrent siphon (I.S.) more open than all the others. My 4" blue is pretty tight, barely opened at all, this is the way it's always been with this clam. My 5" aqua keeps his I.S. opened ever so slightly and to me this looks "right". My biggest 6" black and green normally is open a bit more than the aqua but this clam has had times when his I.S. is so open I can see his insides (they're coloured too!) and a few days ago he gave me a scare by gaping for a whole day. He's gotten over it though. Whew!

Would it be safe to say that individual clams, under nonstressful circumstances, have their own peculiarities in how open or closed they like to hold their I.S.? If so then perhaps it just takes a bit of time to get to know what is normal for each clam.
I think you are on the right track. Individual clams have individual personalities. That may be why it is hard to give any real absolutes as to what is gaping. Maybe it is just "opening more than is normal for that particular clam" It makes it hard when you have a new clam, with no established patterns, though.

When mine has his IS open a lot, and I walk by the tank, it closes right up. (amazing, actually) I think in true gaping, the clam has lost most of its muscle control and can't contract or close up.

Someone had posted a cure for clams in that state is to tie them shut temporarily, so they can heal.
Maybe, if someone sees many clams in the wild, they can chime in here and let us know what is the most common of healthy clams in the wild. I assume clams are in different states of atrophy once they reach our tanks and some may never fully recover, yet remain alive.
One thing I always wondered about clams in the wild is how do they stay upright? In our aquariums, if they fall over, we set them upright, so they can still soak in the light. In the wild, if they fall over because of a fish, current, whatever, I can't imagine that they could get back up again.