I agree with above. Def not a hydno. I would say that it's hard to say exactly with the size of the frag. But I would lean towards a slimer of some sort. Once it starts to grow, the growth structure and form will tell us more.
i have to agree with the slimer polyps and build are almost exactly the same, but the color is something else yellow skin and green blue polyps is this a pritty regular thing for a slimer?