New crocea where to put it

[vlamingi3]

They were all on the sand the in the store and I guess that is o they they dont attach to anything. So where should I place it it is under a 250 mh bulb in a 20 in deep tank.
thanks

 

[Fish-o-holic]

What kinda light was the clam under in the store?

 

[vlamingi3]

one metal halide that was atleast 20 inches off the waters surface. The tank was shallow maybe 12 inches deep. Not sure of the wattage