anemone crabs, parasitic or symbiotic?

[Wiz]

My gbta was my first nem. Had him a year. Split and sold the clone. A while back.
I got an anemone crab a while ago. Thought it would look good in my rbta. As usual it did not like my plan! So it hosts my gbta. Over the last month or two it has become obvious that the gbta is suffering. I could not figure out why. It came out less and less until it barely ever comes out now. The tentacles have gotten shorter and one side of it appears to be turning white. :-(
I could not figure it out. So I've been spot feeding it more to try and recover it. Just today I hit it with some mashed pellet food and the ceab jumped up and started wating. After the food cleared the crab started chewing on the nems tentacles. I don't know if it was eating the food off or actualy eating the tentacle. But it dawned on me that the decline started about the same time as the crab was introduced. I have 3 rbta in there that are fine.
What do yall think? Here is a before and after.

 

[Wiz]

If you look you can see the green in the crabs mouth:-(

 

[Rob.D]

I would remove the crab to see if the BTA recovers....

 

[Wiz]

Update:
I removed the crab about two and a half weeks ago. And the nem is improving. I'm bummed. Really liked the combo. :-( glad I didn't lose my bta though.

 

[Wiz]

Update. He now has completely recovered. I wound up getting rid of the crap. Too bad.

 

[Untamedrose]

parasitic or symbiotic...there is also another option commensal. Where ONE clearly gains from it....and the other isnt so much harmed but also isnt helped..least in the wild.

But I think when it comes to these kinda crabs, and clownfish. The size age of the anemones they are going to mess with in the wild....

OK rambling random in the middle thought... I very much believe that dogs are good for kids, and kids good for dogs.
But you add a 5 pound dog to a 40 pound kid...and your likely to end up with a very nervous unhappy dog. Who is more likely to bite the kid then protect it. Look it up small dogs are the worst for small child bites, most small dogs are turned in to shelters b/c of snapping at little kids... why cause the kid hurts it over and over again not intentionally in little ways. Similar a 120 pound dog, is going to just bowl through a 40 pound kid.(lived that one my grandparents had great danes...)

Why would we assume that a 3 gram fish or crab could host in a .5 gram(wet) anemone...a 6 gram one sure but.... (I'm seriously guessing at the weight of anenomes here but think 3 inches vs 12)
I dont think we are really realistic with the size differences in our tanks vs wild on this.

 

[Untamedrose]

I KNOW my female clown is stealing food from the anemones, she's never feed it...but ripped food out of mouth yup. I'm pretty dang sure she made my small one(3.5 at best) split....and that she herds them together so she can sleep in between. Cause they have tried to move, she batters the side away from the other and by bed time....she's got them together again perfectly spaced for her.
Been going on for a few weeks now. Anemones seem ok(colors good, eats, is bubble tipped and open most of the time) but I'm seriously thinking about ordering another Large one for her. Maybe even out the bullying of the anemone pillows here.