Mine moved down and partially under a rock after almost a year of being content where I initially placed it in the tank. I ended up having to reaquascape....move the (fairly large) rock it was on to get it back under the lights. By the time I did this it was half bleached. Thankfully it has once again stayed put, the colour has returned and I'm able to feed it silversides every other day. While it was hiding, I did my best to keep an eye on it using a mirror to get a better look. When I noticed the bleaching, I knew it was time to do something since it wasn't moving in the right direction on it's own. Rather than try to pry it loose, I chose to rotate the rock.