[AquaAddict]

How about a Goby? esp. a yellow Watchman Goby which is also good at sifting sand and keeping it clean (just make sure your rocks are stable). Your lawnmower blenny should have enough room to share.

Two other choices are Black knobby Sea Cucumbers and/or Neris Snails to do the same thing. You won't see them but they will be good for your sandbed because they burrow right down in it.

Once you have added more Chromis,it might possibly now be a good time to add a dottyback as it looks as if it is too late now to put in the more peaceful fish - not a bad thing because a purple dottyback would be beautiful. Ask your lfs if you can add more than one since your tank is so big..

AquaAddict
PS oh yes, it is possible (not sure) that a Mandarin might not do well with the lawnmower or the 6-line around. check with your lfs.

I hope this helps.