Oscar suddenly ill? please help.

[Hasil]

So Ive had a little oscar for a few months now, and he is the most agile friendly fish, he loves when I come into the room and when I feed him he jumps for his food, but two days ago he suddenly started acting mopey. And now he stopped eating completely, his colors are still vibrant and he looks fine, I can see no signs of disease or parasites but he just floats around by the surface and backs off when I come up to the tank. I checked my water several times, ammonia is 0 nitrate and nitrites 0, its been cycled well for a long time, the temperature is 77.5 and I do water changed every two weeks with filtered purified water. I don't understand what could have possibly happened? I did remove algae from the driftwood in the last cleaning but I doubt he would still be upset about this...

[Aiken Drum]

Please take a read through the "unhealthy fish" sticky and provide as much detail as possible.

https://www.aquariumadvice.com/forum...his-32451.html

I will say your water parameters are essentially impossible. Nitrate is the end product of the nitrogen cycle. In a cycled tank you should see nitrate, in an uncycled tank ammonia and/ or nitrite should be present depending on how far progressed your cycle is. Seeing nothing is a bit of a red flag to me, and could mean you have a water quality issue you arent aware of.

The only way to realistically get zero across the board like that is if you did your water test immediately after a near 100% water change and all you are effectively testing is tap water.

What test kit are you using? Make double sure you are testing correctly. If you still see zero everywhere get a 2nd opinion.

Im not an oscar keeper myself but my understanding is they are very fussy about water quality. They need pristine water and a very clean substrate (or bare bottom) and a water change every 2 weeks doesnt really provide that.