My babies Tridacna maxima, two of them, opened normally, even better than in store. One of them wandered a lot, until found the place away from flow, the second was placed in this place too and never moved.
Mine prefer to be:
- in the low low, mantle is not moved by flow, actually good flow, but around and away from it (not far from 150 gph pump),
- intake opening oriented away from flow, under angle, up to being perpendicular to the low flow,
- the byssal opening is protected by the rock or (now) half of shell,
- on the top of LR "mountain peak", close to the PC lights (72W for 10g tank, plus direct sunlight - southern window).
That what they choosed and the light is all I'm providing while they are small.
What light do you have in the nano cube?
I plan to move my clams in 12g nano-cube, the place likely will be at the top in the middle of the tank - lowest flow around. Light will be also 70W, but MH and the same sun.