Blue Hippo Tang keeps getting ich.

[joe pooh]

I picked up a small Blue Hippo Tang 3 months ago. Put him in quarantine for 3 weeks treated for ich and then put him in the main 130 gallon tank. 5 days later i see ich. Back in to quarantine for 3 weeks and treatment. In the main tank for a few days and more ich. back into quarantine. it spent 3 cycles in quarantine and is back in there again.

All other fish unaffected. 2 clowns, potters angel and a sleeper blue dot goby.

*the temp fluctuates a bit as i do not have a chiller, and the salinity changes a bit too as the water evaporates. but again, all other fish are unaffected.

Don't know if i should just give up on this guy or what?

ideas? advice?