Sick regal tang. Please help.

[saltyair]

check your parameters - sometimes a fish coming from an other system can be use to levels not in the "normal ranges" Also since it did live for a week or more - what other fish do you have? Might have been a conflict.

sorry for the loss - IMO hippo's are not finicky if parameters, tank mates and food is stable.

Remember hippo's in the wild eat mostly planktivorous invertebrates.