Hi guys, I'm new to the forum and just started a new oscar tank. I have a 60 gallon that has been running now for almost 2 weeks. I noticed that my 2 inch tiger oscar had been active from day one except for last night and today. He sits at the bottom of the tank or sometimes is sidelying. He does move from one spot to the next but I haven't seen him swimming around like usual nor does he rise for feedings. My other 2 inch oscars are active no change in behavior. I inspected the little guy and have not seen any physical signs of problems or breathing problems. When I do approach the tank he doesn't flinch. I did a water change last week and made sure the temp matched before slowly adding and didn't notice any behavior changes in the days following. I also did a water test today and my ph is 7.5 which is what it's been since i started the tank, ammonia is at 0ppm, nitrite is 0.25ppm, nitrate 10ppm. The temp is at 24-26 degrees celsius. Do I need to remove him now and place him into a hospital tank?
Any advice would be greatly appreciated...should I be worried?

Assuming that this tank didn't contain any fish before you put the Oscars in, it hasn't been running long enough to be cycled properly. Your ammonia is zero which is good, nitrite is quite high. You also have nitrate readings which is a good sign. If the fish breathing heavily? I would advise you to get some prime, it is manufactured by seachem, this will help detoxify nitrite and ammonia. It's difficult to say why you're asking is behaving like this when the others are okay. What you need to do is make sure that you don't have any toxins present. So if you could tell us if this is a completely new setup, it will help us help you

Hi OFL thanks for the speedy response and for the advice for the prime! My tank is new and what I used to cycle it was a product by Tetra called Safestart. I've had friends that had used the product with success and had recommended it. None of the fish are breathing heavily. Should I do a water change soon and do it weekly to keep toxins low? I don't think I'm overfeeding them either, I feed them once a day and they eat what I give them quite quickly without leaving any leftovers. How could my ammonia levels be fine and my nitrites not and could this be stressing him? I remember reading how salt may be beneficial in certain circumstances for nitrite poisoning, could this be the case for my tiger? Perhaps the old fashioned way of cycling would have been the best bet

since you a nitrate reading this would indicate that you have some bacteria to convert from nitrite to nitrates however it appears that you dont have enough yet. i would recommend a 25% water change every second day until your ammonia and nitrites drop to zero.
i would leave your oscar in the tank and keep testing before every water change.

Thank you so much necromancer4 I feel good about the water change advice, I'll be sure to put in the work and ask for help as I go along!

just an addition to what neco & OFL said,
please check your tap water too. there are times
that tap water contain ammonia & other toxin. some
people stock first the water in a bucket overnight
to stabilized before putting it to the tank.
newly set up tank usually requires 3 to 4 weeks
before fully cycled and ready for fish. in your
case, you have fish from the start.

do as what necro had suggested to meet the required
water parameters for oscar fish keeping.

good luck

the bad thing about that safe start stuff is that it doesnt produce the beneficial bacteria that lives in your filter and other surfaces. it'll make your water good, but as soon as you put fish in and they poo, theres nothing in the filter to remove the ammonia and such the fish produce

Thx PAUL and MetalHead88 for the info and feedback =)....I guess I had to learn the hard way =/ I'm also wondering why safestart worked for my friends and not for me. I did a water change the other day and tested my levels again. Ph 7.4 slightly improved. Ammonia, nitrate, and nitrite levels are now down to 0ppm. My latest problem is that now my water appears cloudy. I did use a buffer to adjust the ph and used Prime by Seachem to remove the nitrites, nitrates, and chlorine. Could any of these have affected my water's clarity? And why only now? Yesterday my water was clear. I did try to find peat moss instead of the powder buffer but my LFS was out of it. What could be causing the cloudiness and what can I do to fix and prevent it?

The good news I have to report is that my tiger is more active now and will rise for feedings. He swims around from time to time and doesn't appear to be struggling in any way. He still does the lying down behavior so I'm going to continue monitoring him.

a nitrate reading is next to impossible to achieve. i would suggest retesting your water and if you still get no nitrate reading try using another test kit.

unless your water's ph is at an extreme you shouldn't worry about it too much. oscars can survive in a wide ph range. where you start to run into problems is when the ph varies to rapidly for the fish to acclimatize.

as for the cloudyness of your tank it could be an algea bloom, floating paricles, or an ammonia / nitrite spike, hence the reason to retest your water.

I've used stability on one occasion and it seemed to work with just a few very small fish. As far as I am aware these products contain free swimming bacteria that is not the same bacteria that you find in your filtration system. The bacteria contained in your biological filter needs both a surface to live on, and oxygen to survive, neither of this will be found in a bottle.
So when you pour it in your tank and add some fish the free swimming bacteria consume the ammonia and nitrite. And I think this stuff will only work with small quantities of fish, and certainly not large fish. If you put too many fish in at once, this stuff won't be able to keep what with the toxins. Used for the duration that you cycle your tank should keep your fish free from toxins. The same goes if you put in very large fish. The only way I've found to establish a healthy biological filter is take your time and be patient. Cycling an aquarium properly is not something that can be done overnight, no matter what these products promise.