Sick Hippo - What is this? Not a parasite

[phillybean]

Thanks for all the replies everyone.

She looked better yesterday, the marking was still there, but has healed a lot. She isn't breathing as quickly as what she was and is eating more aggressive than she was before as well.

Every second day I soak Brine and large Mysis with Cyclopeeze and fresh garlic, which gets fed to the tank. On the days I don't do this, I just feed a cube of Mysis. The hippo won't eat Nori! I've tried sheets on PVC, tied to a rock, mag float and shredded and put in the tank. She goes crazy over Formula 2 Flakes though.