My oscar is about 9 to 10 inches. He is normally very active but now he is just laying on the bottom of the tank on his side. He will not move even when I put my hand in the tank. We have not done a recent water change and the temp has been 76 to 78. PH was low (below 7.0) I added PH. But still no change. What should I do. Ive only had him for a little over a month, so I not sure how to proceed.

Do you know the water parameters of the tank i.e. Ammonia,nitrite and nitrate readings. How long is it since you have done a water change? How big is the tank and what sort of filtration do you have? if you can answer these we may be able to assist you . Having said that it is not uncommon for Oscars to lie on their side.

As Steve says, Oscars do sometimes lay on their side. However, from my experience, they don't do it for a long time. I can't really add much more to what has already been asked apart from asking whether or not your fish is breathing heavily? Is it reluctant to feed? Please let us have those water readings, they are absolutely vital, it's very difficult to help you without knowing what condition your water is in. Please also tell us how big your tank is and what kind of filtration you are using.

The tank is 55 gallons. nitrate were 20 or below nitrite read 0.5 ammonia was o. i have 2 water filters aqua clear with an ammonia filter and foam filter and an aqua tech for a 60 gallon. last water change anout 2 weeks ago. this morning he is moving but he still flops over to the side. He has been eating.

Okay, nitrite is rather high. This does happen occasionally and can sometimes go away as quickly as it appears. Reduce feeding until we can get this problem sorted out. I would suggest you feed every other day, your Oscar sounds as if it is an adult which means it doesn't need as much food.

Carry out a 25% water change every other day until your nitrite read zero. I would suggest that you get a product like prime manufactured by Seachem, this will reduce the toxicity of the nitrite and take some stress of the fish. This could possibly be why your fish is acting the way it is. You didn't mention whether the fish was breathing heavily or not.

I would also suggest that you need to do water changes on a more regular basis

Do some large WC, maybe add some ammo chips or bio-zyme, whatever you can get your hands on.

He was barely breathing and not moving his fins. What I did do was a water change. I have been using Prime when ever we do a water change as well as Stress Coat. I also had a package of General Cure which I put in the tank. He is now moving about the tank and is swimming straighter. He still tilts to one side a little. I'll do another water change tomorrow.
Thanks so much for your help.

Good. Continue with the large WC etc.