Fish can have hith for years before you will ever know it. Again hith is not a diesease and your fish does is not infected with hith (hith is a symptom, I'll explain in a minute)- it has a parastie, bad water, bad diet or a combo of all 3. hith is not the problem in itself it is merely a symptom of the problem. You need to figure out why it has hith, what exactly are your water params? Do you only feed it pellets and not other things? Does it have heximita(sp)? Here is what I mean by hith not being the disease alone. When you get a cold, you develope a cough as a symptom of the cold, hith works the same way. If you have HITH it is a symptom of something else such as bad water quality irritating the sensory system, allowing a parasite heximita which causes the symptom of hith. You can try to do water changes very ofen and keep your water prestine clean. You can treat it with Metronidazole, however I can't say that it will always work - it has in come cases and has not in others.