Greetings from Canada

[Mentat]

...I was wondering if I could pick your brain about something? I'm having an issue with my female Tiger Oscar "Dexter". She's about 3 years old, and seems to be in a "funk". We aren't sure if she's poorly, or just being moody.
Basically, she's not interested in eating much (BF can't remember the last time she actually ate something), she spends most of her time either sitting at the bottom of the tank (like they do when they sleep), or sitting at the top of the tank and she looks like she is breathing hard. We have the Rena 400 air pump in that tank with two large ball air stones. None of the other fish have labored breathing. ...
Her diet consists mainly of: buggies, worms, cocktail shrimp, some cichlid pellets and fish flakes

What are tank's water parameters (temp., pH, ammonia, nitrites, & nitrates) and water change schedule? Breathing hard could mean an external small parasite infection like Oodinium or Costia; but in a tank it should spread to other fishes. Other possibilities are internal bacteria or parasites or maybe something natural like old age. Although wild Oscars are strong fish; they have been inbred so much by industry, their immune system is affected and many have become magnets for all kinds of fish diseases like HITH (Hexamita) you mentioned.

[Sandy Bear]

Well, I'm sad to report our "Dexter" died today. I'm wondering if she had that Lateral Line erosion, but I haven't been able to find any good pictures of it to compare. She was missing some scales along her lateral line, but I'm not sure if that is just some damage that she sustained from from the other fish when she was being inactive. Her behavior reminded me a lot of what our Charlie was like when he go Hole in the Head.
Anyways, BF has been really busy with school this year, and hasn't been diligent with the tank, so I think I will be helping him out with that now.