Xenia- Torn at base?

Picked up a decent sized chunk of xenia about two weeks ago and noticed yesterday it was lifting from the rock it was anchored to. It is in strong light, high in the tank and in fairly strong flow.
I thought it was in too much flow and was lifting due to the current. But closer inspection shows it looks like the base has been torn.
(Red circle)

There is a section directly above that which appears to have been chewed.
(purple circle)

Possible culprits:
small gorilla crab
peppermint shrimp
Yellow tang
Hippo tang
Foxface
Overthe last six months I have made two or three attempts to raise xenia, only to have it disappear (most often chewed in half) over the course of a few weeks. I have heard they can be fussy if water parameters aren't great, and I am a CHRONIC overfeeder, so my nitrates were high when I first got the coral. I have cut feedings to every other day to make sure I keep nitrate levels down.
So someone is now extra hungry.
I've turned off the power head that was helping to lift the base and tear more, and intend to try and find out who the culprit is.
Can you think of anything else that may help?
THNX

Flickr: dearmissavery's Photostream

 

It's wanting to move, if you have a small frag of live rock' you can lay it near it will crawl and separate from the main
stalk from its parent colony, meaning it wants to "split" in two,
( this is how they move they will actuly let loose of the rock and tend to move in the direction of water flow.)
It wants to make two for you , lay a rock near the piece thats separating and watch !

As well xenia can handle some nitrates and they do tend to do better in tanks that are fed more than less.
( xenia do poorly in a nitrate/phosphate absent tank , and they LOVE light the more the better it seems )
Now im not saying xenia can handle HIGH nitrate levels , but they do very well in a tank that has some in it.
LoL , turn your power head back on .
how many ya want ?.lol

 

Yes as Mission says it's bout bullet proof, I think ya could take it out roll it on the floor and let the cat play with it , then throw it back in the tank and it'll grow. LOL

 

i've never heard of any type of fish to ever eat xenia.it has to be something about the water or light

 

Where it's sitting I can't put another rock along side. So it looks like I will be fragging it tonight.

I realize xenia doesn't want zero nitrates, and that some nitrates are beneficial. (The most impressive display I've seen of Xenia was at a LFS that bragged the tank used a bio-ball filled wet/dri) But I do have to get my nitrates down, I am seeing too much algae. I just need to monitor better than I have been.
Thanks for the help everyone