I removed my gravel with a big pipe doing a water change, then added the well-washed sand (carefully!) with the fish in the tank, no problems. Last night I syphoned all the sand out doing a 50% water change and now just have a bare bottom.
Mine has become an krillaholic and refuses shrimp if krill is in the tank. And to think that 1 month ago he wouldn't even touch it and now eats out of my hand.