clam can cert'ly attach to the bottom. np. for me, i'd place some small, 1/2", rocks around it. maybe it'll grab onto those. then moving is easier. if he gets enough light on bottom, no probs. i have a few unattached little clams.moliken, I hope you stop back by...now that the clam has pretty much forced its way down to the bottom, I'm a bit concerned that it won't do well long-term on a surface where it cannot attach (the glass). It has stopped jumping around quite as much, I think. Will lack of attachment be a real problem?