Hello.

I've been having issue's with my oscar - oscars.
Originally i had 2 tiger oscars, very small , about 2 inches in size , one slightly bigger than the other. The small one died, ( acting very odd hiding under a rock for weeks then i found it stuck to the filter. My concern now is that the one i have left has gone off its food and is now sitting at the bottom of the gravel by the filter pump, all the time! and somtimes when approched , lies on its side. this has been going on for about week an half. Ive noticed that he does quivver his tail now and then and he is slowly opening his mouth. I know that you guy's are gonna tell me that a 35 imperial gallon tank is not big enough for a oscar. however i do have a larger one ready for later use. The set up i have is overhead filteration system, which the filtered water goes through a series of media and carbon filters. 1 large air brick. no live plants, and the thermal heater which is about 27-28. Now, i had made sure that the tank has been cycled, and i have had to add de-clorinater too.Ive been using API test strips to test water, and it seem my PH is low, so today i purchased some Ph up. ( awaiting results ). ive only fed this oscar the small pellets at the moment. Looking into crickets and blood worms and meal worms. can anyone help me with this problem, as its driving me nuts, and i do care for this fish, ive put a lot of time and effort in this, i'd like to be a happy oscar owner and do the right thing,

Regards
leeroy

Please do not try and adjust your pH unless instructed otherwise. You're more likely to make things worse than good.Please tell us what your pH was before you adjusted it?

We would also need to know what your ammonia, nitrite and nitrates is

GH 120 kh 180 ph less than 6 nitrite 0 nitrate 0

i was instructed to up the ph as it was low.

regards
leeroy

oscars are able to thrive in a wide ph range(6-8) as long as its stable. modifiying your ph levels is a tricky process that really should only be attemped by experienced fishkeepers. as long as your ph is stable you really shouldnt worry about it much.

as for your nitrate reading of zero this has me a little concerned since in an established tank you should always have a reading for nitrates. also i noticed that you didnt post a reading for ammonia, which is the most toxic of the three.
if you could retest and repost your water parameters (ammonia, nitrite, nitrates ph and temp) it would be benficial in helping you with your tank.