I'm so glad I can get back on here...

My O has been an entirely different fish for the last week. He went from being lazy, sometimes almost lethargic. He would only really get excited if I was feeding him, or if I had cleaned his tank. He was a constant eater, wasn't picky at all. Other than a normal water change, nothing was done to the tank.

NOW, he is very destructive. He is hitting himself against the inside of the tank. He sometimes smashes himself into the gravel. He swims about half way down the length of the glass, swims up and then almost turns upside down completely and then he will almost hit the bottom. On top of his head almost. He will open his mouth really wide and swim directly into the sides of the tank. If this was just an occasional event I wouldn't worry. But this has been going on since last thursday. He has only eaten small amounts of food since then as well. This behavior is almost constant . Doesn't matter if I turn the lights on or off.

He's in a 55 gallon all by himself.

ph 7.6
no2 0
amm .25
no3 10ppm

It could be down to your water conditions, unfortunately they are not very good. Ammonia and nitrite should be kept at Zero at all times, nitrate levels shouldn't exceed 40 ppm, however to lower the better.

You need to work out why your water conditions are poor at the moment. How many fish have you got? Is your tank cycled?, how often are you carrying out water changes? Are you cleaning your filters? how much food are you putting on the tank?

Poor water conditions are normally the cause of many problems. It is quite important to get an understanding of what is going on in your tank.

how big is your oscar now?????
if smashing is something like pushing everything or
trying to bite anything inside, scooping all substrate,
be ready.... it is just maturing and showing normal
behavior. put a big slab of clean rock, or inverted
porcelain plate, or clay bricks and it will clean it.
you do have a maturing oscar.

if none of the above sign, please double check your
water parameters.

I will do a water change. Unfortunately I didn't see this site before I bought my fish, and he has been subjected to the cycle. But it has been since the beggining of march. He's about 6 inches now.

6 inches or 6 months could start maturity habits....
if no water issues to correct, your oscar is acting
normal.

I'd just like to add that my oscar is also around 6 inches & he did the same so you are not alone, after I changed from gravel to sand he kept digging up holes in the sand & the aggression stopped. like paul mentioned I guess this is fairly normal, unless its a issue with your water.

Did he also stop eating?

no, alwyas hungry...
if your o stop eating, the more you need to check
water parameters.

it is normal for O's to go off their food every now again but this usually dosnt last long and they start eating again, however with the other behaviour your O is displaying it may point to something else...
do you have substrate on the bottom of your tank or is it glass?

gravel

it almost sounds as if your O is trying to scare off his reflection, which would be quite possible if he is at maturing age.

he may think that his reflection is another O in the tank

no digging or scooping????