Hippo with bad ick

[kien]

That doesn't look that bad to me, yet. If your hippo is still swimming around actively (not lethargic), eating, generally acting normal (minus occasionally scratching on rocks), then I would just observe your tang for now. Perhaps soak some food in garlic extract. If she's healthy and behaving normally then she should be able to recover from it.

Your other alternative is to go full-on attack mode, take your Tang out, put her into a quarantine system and begin treat with one of the various treatment methods (meds, hypo salinity, tank transfers, a combination of..). Lots of treatment options if you search the forum for "ick." I personally would not recommend them but it's up to the hobbyist to decide which road to take with the ones presented in front of them.