i dont reccomend adding a hippo tang to a 75 gal at all although a tiny one will have plenty of swimming room for some time the smaller ones tend to have less survival rate med sized 4-5 inch tend to have better rates but they can stress easily, these fish do get large(over a ft) they get ich every time you move them.if your going to qt him i make sure your qt is large enough to keep stress down like a 50 gal they cannot tolerate cramped quarters(its a death sentence)if you realy want one its your tank i dont reccomend thats all.but if you decide to go on with getting one set up a 50 gal qt and coppersafe the tank add some LR(you cannot put his back in the main tank at later date) and fresh magro algaes for grazing naturally add a hang on back filter system if you run the tank with coppersafe carbons can be used if the carbon pack has been used for at least 6 days.you will also need a small powerhead lighting and such.you basicly need to set up a whole new tank if you want qt to be the least amount of stress as possible as qt is used for 30 days minimum 21 days.the coppersafe will kill all forms of paresites that could be present on your new fish not just ich.here is a pic of my qt with a newly added majestic foxface.(also related to the tang family). feeding the new commers is the hardest part this is why fresh macro is very important.ps first 24 hrs in tank i add melafix w/o carbons then day after do the coppersafe
also the best foods for your new tang (pellet form)thera+A non medicated antiparesitic formula by spectrum
flake: veggie flake or kelp flake by omega one
frozen prepared foods:emerald entrese,formula 2
as a treat not a staple diet:seaweed sheets(i use seaweed selects) red variety has the most nutrients of all the sheets.the fish need to be fed 3-5 times daily in small amounts each time. i also add garlic extreme and selcon directly the the tank water at reccomended dosage to boost imune system. good luck