i have a ( baby ) oscar roughly 8 inches in length and about 8-9 months old.i have recently noticed its one eye starting to swell up.all water checks have been done and are fine and the fish has shown no real change in its feeding or behavior habits.any ideas????????

It's not exactly a baby, it's nearly an adult actually

There is a possibility that your Oscar is developing Pop-eye disease. Start doing extra water changes. I would do one every other day, around 20%. Pop-eye disease is often caused by poor water conditions. Make sure you feed your Oscar on only good quality food. Get yourself some Hikari or Tetra pellets, you can't go wrong with those.

There are various medications on the market, one that I would recommend is called myxazin. This is one medication that can be used for Pop-eye disease

Myxazin is great stuff. Both the eyes on my jaguar swelled up and went cloudy. I treated with myxazin. It took 2 weeks for the eyes to get back to normal and boy did that jag eat once he could see the food(he didnt eat for 2 weeks as he couldnt see)

Well, there you go, a very good endorsement for the product