Mantle extension, is this much normal?


New member
I have a 3.5 inch crocea that is extending its mantle out about 1" all the way across. Color and consistency are great, it just seems that it is a little too far extended. It is not gapping the shell , just extending the mantle.

I am concerned since Knop lists this as a possible stress factor.
It is 24" from 175 13K halide, I will move it up at end of week, I have only had it four days.

Thanks for helping a first timer,

Here is a side shot I can post more if need be.
The mantle is a good shade of blue with nice highlights, not brown as the pic suggests. Here is an actinic top view.
It's a sign that the clam is mighty happy and you are an awesome aquarist.

Crocea clams can have some really wild mantle extension. Stronger than all other Tridacnids.
just like project reef said...croceas extend a LOT!! mine extends WAY beyond the shell...a good 1-2"...pretty cool to see

Just in case you wanted some more opinions...

I too think you have a happy and healthy clam! My largest crocea has very wide mantle extension.

Also, if you ever suspect stress, look out for gaping of the inhalent syphon.

I got it from "The Farm" at It is run by Blane Perun and he has an interesting selection of specimens for a small setup. He is in Pennsylvania if anyone is close. He has a map on his site.

Settling Down?

Settling Down?

It seems to be sealing itself to the rock now. I looks like it has put down a layer of silicone uder its shell. What is the difference between what I am seeing and the byssal threads? I will try to post some more pictures tonight.

Thanks for the encouragement,
Here is the best view I can give!

Here is the best view I can give!

I believe the clam to be attached. I moved the rock to get a top shot and it did not move an inch. It had very good reactions, retracting and coming back out almost immediately. It was even glowing down inside where the light would hit inside with the mantle open. I could not get a clear shot though. It's amazing how God designs organisms to maximize their resources. Take a look and let me know what you think!