HITH on oscars caused by low PH ???

[guppy]

The true cause of HITH is debated, the organism that activelly involve is a protozoa called Hexamita that is very common as a low grade intestinal infection of cichlid and other fish, much like E. coli bacteria live in humans. The sensory pits on the fish get irritated and the tissue lining them starts to break down, It might be due to long term nitrate exposure, dietary imbalance, reduce resistance to disease, high bacterial loads, whatever. Then the damaged tissue is colonisee bt the protozoal who eat the damaged tissue and release digestive enzymes that damage more tissue allowing the infection to spread.
A human analogy is take a human, lock them in a room and feed them junk food while also giving them inadequete means to stay clean. Then when they start to get pimples and boils expose them to a staph bacteria in their wash water. Then watch the pimples turn into jungle ulcers. Sort of like that.
The meds, mainly metronidazol, used for HITH are anti-parasitical rather than antibiotic.

 

[hood9999]

What guppy said

 

[xice99]

I'm new here, what is HITH ?

i have 4 big oscars in my other pond (among others), each different variety, never had any sickness, and I change my water in our pond every 4-5 months. (usually when I see lotsa feeder fish have parasites, that would be my cue to drain/change the water.)

my oscars never had parasites tho.

 

[Miles]

more likely it is detritus deep in your gravel

After working at PetSmart for so long, and seeing so many cases of HITH w/ Oscars, this is usually the culprit.

Your water is extremely Acidic because your tank is dirty. Oscars are dirty fish. Take a spoon and stir your gravel, if a brown cloud of crap comes billowing out, you have a problem.

Your 'varied' diet might of been overfeeding the tank..

What are your nitrates at? Above 100ppm?

I just think some very thorough cleaning is in order, followed by some meds for the Hexamita... and all that other good info that Guppy gave you!