clam care

Hello! I'm a new clam dad and I recently picked up this Derasa clam about 3 days ago. I love this thing to pieces but I noticed its Incurrent Siphon has been gaping the past two days... I've been watching it like a hawk to make sure it didn't show any other signs of unhappiness but I can't...

I am thinking about a crocea or maxima clam for my 16 gallon biocube when my tank is established. I have some questions. 1) Which is easier to care for? 2) Could I even be able to put one in my biocube?