I had 2 tiger oscars that developed HITH. One somehow jumped out of a 2 inch opening & committed suicide on my kitchen floor in the night & the other I had to put to sleep which was very sad! I tried to get them better for several months before they died. After they were both gone I cleaned the tank I thought very well. I didn't change out the gravel, but I did rinse & wash with mild soap & water several times.

I went & purchased one tiger oscar & one red oscar, both gorgeous & very healthy. After having them less than 2 months they both have HITH & the tiger oscar looks horrible. It spread so fast on him it seems it was overnight!!

Is it possible that some of the infection remained in the tank & infected the new fish? If so is it possible to ever uses this tank again if cleaned properly? What is the best way to clean a tank after it's had infected fish? Bleach? Other chemicals?

I really love my tank & it's a unique shape with matching stand. I would hate to get rid of it, but I refuse to buy anymore oscars until I have this resolved.

Any help is very much appreciated. Thank you

hith is usually brought on by poor diet or poor water conditions. do you have a water test kit and if so what kind of reading for nitrates were you getting before your water changes.
also what is the size of your tank and are you cycling it properly before adding the oscars to it? oscar are a poor choice for cycling tanks because of they are prone to hith.

I haven't even had them 2 months.It's a 60 gallon tank (for now) & my water tests have been great. I don't understand.....

what are the actual numbers for ammonia nitrite and nitrate. some definitions of great are good for some types of fish but not others. also how long has yuor tank been established