I have 2 Oscars in my tank, they have either been fighting or courting over the last few weeks. I woke up today and when I turned the lights on, I saw several large white fuzzy clouds floating around! Is this a sign of breeding or some other issue with my tank? Never saw it before...

Can you post a pic? Remind me again, How old are your Oscars, how big is your tank, and filter? And can you test your water please?

I don't know exactly how old, but I got them when they were 4 and 6", in the 9 months I have had them they have each grown an inch or so. Tank is 55 gallons (I know now that is too small really) and I have an HOB filter. They have been lip-locking and tail-shimmying for a few weeks now so based on what I've read that is likely courtship behavior. I have also been dealing with an ammonia spike lately, treating tank with Stability and also ammo-lock and frequent water changes if that helps in your assessment. I tried to get a decent pic but most of the slime-like clouds are gone now but you can still see some wispy pieces stuck on some plants/ornaments.

anyone else have any thoughts?

I don't know but I'm interested in what the others think, I had the same thing last week and lost both firemouths and both pitcus catfish. The Jewels and Jack seem to be fine though. Mine happened right after a water change, did yours?

4 and 6 inches long at 9 months old is way too far from spawning.
besides, spawning never had any white fuzzy stuff in the process.

do you have any new things that had been introduce lately...say
driftwood, plants, or rocks.... cottony white stuff sometimes
is a product of slime and waste that binds in water.....

but to be sure, we need to know your water parameters