I dechlorinate the water everytime i add fresh water. I found a big enough bucket that ill be keeping her in, does she need light source? Ill make sure to clean every two weeks. I havent gotten to research alot about oscar necessities but the tank i have is way bigger than what they had them in.
She should be ok with regular light, you don't want to stress her. One thing that happens is if water quality isn't good fish will pop up with bacterial issues like sores, fin rot, excess slime and redness on the body and eyes. Sometimes it takes awhile or it can happen suddenly. Oscars are clumsy and can scrape themselves. All decorations should be smooth or soft. No jagged edges or rough surfaces.
Water can look clear but be full of toxic waste the fish produce. That's why water changes are so vital.
Do your oscar research asap. There's good and bad information online. But to make a long story short:
90+ gallons for 1 oscar
125 gallons will work for 2
water change out once or twice a week
keep mechanical filtration clean by washing in old tank water
don't touch the bio media that holds the good bacteria
get a water testing kit
whatever you do a maintenance schedule is essential with oscars. Good luck!