My tank is a 37 gallon marineland biowheel. I have a tiny oscar. Yes, I realize I will need a bigger tank. This was a rescue fish and unexpected. I also have an in tank whisper filter in there, rated to 40 gallons.

Water test results. I did a 30% water change 2 days ago, a 50% one about 10 hours ago. These are my results.

PH-8.2
Nitrate-5.0
Ammonia-0
Nitrite-5.0 or maybe slightly higher.

What can I do? I changed the water, I also used some bottled bacteria and water purifier.

It will take time for the biowheel to cycle. It is GREAT that you put in cycled water, but it takes time for the surface of a given biofilter to get a viable culture started. How long has the tank been running?

Also, oscars are always messy fish, and I have always been a proponent of over-filtration. Is there any way you could get a second filter of the same size?

I have two filters running. The biowheel 3 in the hood. It has a filter cartridge as well as the wheel. I also have an in tank whisper filter for up to 40 gallons. So I am filtering double.

How long has the biowheel been running?

A week today. I had the filter, but had to get a new wheel. I can see that things are improving, I guess my main question is will my fish be ok with the nitrites? He seems completely unstressed.

The other two filters have been going about 3 weeks.

Unfortunately, nitrites are not much better than ammonia to a fish. You should try some "prime" or other tank establishment liquid like "stability."

An expert I am sure will give you more in depth advice, but, I'd start with that.

This is part of the tank cycling process. When you have to replace biomedia thia can happen

Nitrite should be zero in a cycled tank. Do daily 25% water changes until your tank is cycled (ammonia, nitrite of zero and nitrate rising). You do these daily water changes to keep the ammonia and nitrite down as these are poisonous to fish.

Got that, 25%. I know I seem stupid about this. I swear I am not

your tank is not fully cycled and the measure of nitrite is probably giving a fake nitrate reading, like delboy said water changes till your readings are better

check this link out for an explanation of cycling

www.oscarfishlover.com/how-to-cycle-a-tank

I would say your tank is just beginning to cycle. IOW, you are converting ammonia to the equally harmful nitrite.

My research has led me to conclude that if you have a nitrite reading, you must subtract that from your nitrate reading to get a TRUE reading for nitrates. If you accept that premise, you have 0 ammonia, 5 ppm nitrite and 0 nitrate.