I found my brand new Flame angel in the very back on my corner tank dead with orange fuzzy stuff growing all over him.

In order to get the carcass out I will need to dismantle the whole right side on my tank!

I don't have a clue as to what killed it but my question is what is the worste that could happen if I just left the carcass in the tank? What is that orange Fuzzie stuff.
Here's a pic of the work ahead should I have to remove the dead flame angel.
