they change shells when they out grow the one they are in. i went my store and saw 5 lg shells in the tanks and bought them. bout 4 days later the red crab changed shells(he took the biggest one i had). it looked huge on him, but thats when i noticed him growin quicker. my smaller white one needs a new shell but wont give up his anenome shell(i think pride is a factor with him).

ya 2-3lb rocks, i took my biger rocks out cuz i dont want him to fall off the rocks n break the glass with his bigass shell. im still concerned about the fact that he can pick the rocks up, but what if he goes roger clemmens on my glass? ill just buy a bigger tank i guess....lol

If I understood what I read awhile ago right, generally fish (especially those who naturally come from a lot of current, like stream/river fish like my kuhlis) enjoy a lot of current in the tank, and most enjoy a good degree of some current. However all fish like to sleep/rest so as long as there are dead spots (like your back corner) however inconvenient to viewing your fish they may be... your set living conditions shouldn't prove too stressful for them. :) Picture no deadspots as yourself going to bed and realizing that your pillow is gone, so you have to suspend your head several inches above the bed all night. (but not quite as stressful) lol
On the other hand if you find that you're experiencing the equivalent to underwater hurricane category 5, even a deadspot might not be too soothing. lol