Yestarday I bought a small flourescent green haddoni which had been at the store for aprox a week after import. It was attached and looked good so I brought it home. It was placed under shade in an area of the sand bed which is approximately 3" deep. It had dug down and attached to the base of the tank after about 15-20 minutes and so far so good. I tried it with a half inch piece of raw prawn this morning which it took and ate. At approx 7:15 this evening I noticed an interrupted string of brown coming from its mouth. This continued up to 8:00. Is this zooxanthellae ?