Like Hank said heat is a big no no in marine.
The hypo ,copper and transfer method are the only 3 true ways to cure marine ich.
The transfer method requires 2 tanks and moving the fish daily for weeks to get it away from the parasite while it is falling off.
In marine ich the parasite sets up shop where it believes the fish sleep so it can re infect them nightly !
No need to use copper with hypo ,I would pick one or the other with hypo being more natural and possibly safer.
You are correct though that if you use copper you MUST have copper test kit. Too much CU and the fish will die.
If the hippo has ich which is fairly common in newly acquired fish the hypo would be my go to method.Safe ,easy and adjustable..
A couple weeks of no spots and thorough cleaning of bottom of tank should be all you need.