Hello, I am new to the forum. I have had my oscar since the middle of August...He has had his odd moments now and again but this past month he really seems off....I have checked the PH, nitrate, ammo, temp....Everything seems normal...I do regular water changes(which he really hates)...The set up I have him in is a 40 gal tank, airpump, new heater, good filtration system....I have regular gravel that I clean out once a week and some fake plants for his privacy....He always eats the cichlid pellets...Loved them..no problems..till last tuesday he stopped eating them all together...Now it seems that he will not eat the food unless it moves(swims). I know I am not supposed to feed him feeder fish but it was the only way I could get him to eat....I dont know what to do....He was sick over the weekend...floating on his side..up near the surface...he pulled out of it though thank God...Any advice? Please...I am new to this....Also, at night time I hear him splashing and banging hard around the tank...When I check on him, he is all bruised.....Ughhh....Help please!

perhaps, your O wants to box with your cat (avatar)
ha ha ah.... welcome to the site.

(quote): everything seems normal....(unquote)

though i am not used to know water parameters, it will
be helpful if you can post the following:
ammonia:
nitrate:
nitrite:
pH;
temp (depend on your location):

splashing and banging is a symptom of distress.
in good water condition, O tends to swim gracefully,
enjoy the foods, and rest at night time (light off)

As Paul asked please post your readings for us to look over. do you have other fish in the tank? We do have a large number of people come to the site with the same problem, oscars not eating. this is very common with these fish. What I will say now is oscars can become very fussy eaters if you spoil them to much. i take it your oscars eating well if you give feeder fish. this could be that it has become used to this food and a few days starvation should work here. a oscar in good health can go many weeks without food so dont worry. I would only do this if it has recovered from any ill looking episodes. if it is still acting ill i would feed it anything it will eat as keeping its energy up is more important. when you get back with the results we may be how to advise more. love the cat.)))

Thanks Marcus for the info...I have only the one fish in the 40 gal tank alone...I ran out of test kits for the nitrate, nitrite and ammonia...But my ph is somewhat low(I just checked it a minute ago after doing a 1/4 water change it was at 5.5 which is up from 4.0 before the change...I am really losing it here...I have tried almost everything I can think of to improve the tank and his health...I even removed every bit of gravel from the tank yesterday and thoroughly cleaned it with hot water sifting it multiple times till all the muck and cloudy water cleared...Still left with an unhappy oscar who sadly comes up to me at the tank and stares at me...I wish he would eat...Ugh....

Thanks Paul for the help....I am out of test kits at the moment..I will be out tomorrow to buy more..

reminder.... don't wash your filter media in tap water
when doing the cleaning. moreover, do not clean them all
at a time (common mistake in cleaning the tank)

Your tank is going to start cycling now. Keep an eye on ammonia and nitrites. You will likely need water changes every other day.

but if you carry out water changes as frequently as that you may stress the fish right out .....that much disturbance wont be welcomed my o,s hate water changes immensely.......just my opinion tho

still better to change the water and lower the ammonia than to not stress the fish and forgo the water changes.

stress "might" kill your fish but ammonia "definelty" will.

i agree !!!!!