Hi everyone.
young 5" Oscar fish in 5.5gal mildly planted, heavily filtered, no-meds, quarantine tank.
Temp 28C (82.4F), ph 7.7, Ammonia 0, Nitrite 0, Nitrate 10ppm, GH 9, KH7.
All measurements with liquid reagents tests.

History:
I brought the Oscar (belonged to a friend of mine) from the LFS yesterday. Spent quite some time aclimating (LFS water ph 6.5, my tank 7.7). The oscar got really stressed in the bag, turning pale and laying down a bit (tilted).
Since I am expecting a 6footer, 145gal next week, and just finished planted fishless-cycling a 29g bow (tall tank) with a surface area equivalent to a 20gal, I decided to bring him home.
I removed some plants that I would like to preserve for later, performed a total water change, kept floating plants (two dense bundles of anacharis, hornwort) and a large sword that is attached to a good size stone. At that time all readings were perfect, except for ph7.7.
The Oscar was placed carefully in the tank, swam for cover and I went to my office. (1:45PM).
Upon arrival (8:30PM) the Oscar was laying horizontally, partly covered with sand. I thought he/she was dead. Fortunately not so!
I have a 5.5gal hospital tank running 24/7 with 3 fancy guppies and fry in it (guppy fry factory/quarantine tank), lightly planted, sand substrate. I set it up with heavy filtration (placing the 29gal HOB in it) then placed the 5" Oscar (might be a little less than five inches actually) in a soft fish net breeder, to create shallow water conditions for him. All night the Oscar remained laying down, barely moving at all, except for breathing ok and normal eyemovement.
This morning (8:00AM) still laying down horizontally. I dropped three pellets and left. Upon return from my office, no remains of the pellets, and although lethargic, the Oscar is moving a bit, tilted most of the time at 30 degrees. I put some (not much) whole bloodworms (in gel). After a few minutes, the Oscar "stood up" ate the thing, and is now back at 30 degrees (tilted). I noticed he/she is moving his/her pectoral fins (last night no movement at all).
Any ideas of what should I expect? This is my first Oscar ever.
Pepe
Santo Domingo

Welcome to Oscarfishlover. I started reading your post and saw 5 1/2 gallons and thought oh no, I'm going to have to inform this person that they need to take their o back to the shop. Anyway, I'm glad that you are getting your new tank soon

The water conditions you have given us are pretty much perfect. However, the tank is grossly too small for a 5 1/2 inch Oscar. Having said that, it's only a hospital tank so it'll be okay for a few days, just keep an eye on those water conditions and feed extremely sparingly. It may just be that the Oscar needs time to settle in. Because your water conditions are good, it's very difficult to put our finger on what, or if anything is wrong. The behaviour that your Oscar is showing is not unheard of, they often lie on their side for a while after being transported in a bag full of water. I would suggest that you leave the lights off in the tank and just observe the fish. If the fish is showing no signs of illness then if you can put into a bigger tank, please do so. It won't be very long before water conditions start going down hill in that small tank. Apart from that, there isn't really any more advice I can give you apart from observing the fish. Hopefully, when it comes down and the stress diminishes, he will be perfectly okay. Don't try and feed him while he is like this, wait until he is swimming around. I would also ask you to see if the fish is breathing heavily. If he has, we won't put it down to water conditions because they are very good. It will probably be stress. However, the heavy breathing shouldn't last very long if the water conditions are good, and the tank is being oxygenated properly. Heavy breathing can often indicate problems such as lack of oxygen, ill health, and stress.

Thank you for getting back quickly.
I feel I have company in stressful moments like these. I barely slept last night keeping an eye on Moon (the Oscar's name). I read your comments, compared water parameters of both tanks (the 5.5gal hospital and the 29g bow) and they are the same as for temp, ph, ammonia, nitrites, nitrates. There is a small difference in GH and KH, but I would render them to be non-significant (both lie within the soft-to-hard threshold). So I put Moon back to the 29gal. After a few minutes (as I write to you) he is already swimming around. As for food, I will wait until late night or tomorrow (I fed him/her sparingly and so far has eaten it all -6 pellets and some whole bloodworms in gel).
This was likely stress-caused due to bag storage/transportation.
Thank you very much!

Oscars often act odd when first put in a new tank, its not unusual. It takes up to a week for them to settle in properly

Update: The Oscar is swimming around but hides -even laying down at less than 30degrees, when notices someone around.

I fed him/her with some whole bloodworms in gel, and is eating well. I followed your directions and kept the lights off, I will turn them at morning.

The tank he/she is in is in my home's office. What a beautiful fish!
Thank you all.

Update: turned the lights on for 4 hours, added some slate rocks, fed with pellets. He/she seems fine so far. Brought a digital camera to take some pics, but since I left the lights off I will wait until morning in order to not cause him/her more unnecessary distress. Water parameters remain stable. Still feeding carefully.

I did noticed that the right side pelvic fin is smaller than the left side, is that normal?
Pepe
Santo Domingo