Test your water and post your perimeters.
How often do you do water changes? What size is the tank? What is the stock? What is the filtration?
It is very possible that your GT's HITH and it's almost certain that it's popped eyes are caused by bad water perimeters.
Alternatively, it's possible your fish's HITH is caused by a nutrient deficiency. What do you feed it?
If you habitually feed your GT feeder fish, then its likely your GT has a buildup of thiaminase which causes erosion of the lateral line by blocking the fish's ability to metabolize vitamin B. If this is the case, you need to ensure you have good water and get your fish eating a nutritionally complete diet.
It is my opinion that you need to find the root cause of the development of your fish's HITH and pop eye and correct that before you go dumping chemicals into the tank.
