What causes a clam to gap?

[ReeferGreg]

I just got a ~4inch crocea for my 90g about 2 weeks ago, and I just noticed it started to gap.

I've got plenty of lighting...2x400w HQI 20K Radiums so it burns pretty white. Water params are all in check.

What generally causes this? At the store it was under 3x250.

Greg

 

[Electrobes]

Just stress. It happens to many clams, but Croceas in particular do it very often, sometimes doing it naturally. Over gaping is something you don't want to happen, but it will definately gape when introduced to a new aquarium.