This is the day I brought her home.
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She was a tiny thing @1.5 inches. She started out in a 55gal. At the 8in mark, she moved up to a 125gal.
For the moment lets worry about getting yours thru this cycle. If you don't have an air pump on your tank I suggest getting one. Oscar's like highly oxygenated water. The more the surface of the water is agitated the more oxygen gets pulled into the water column.
Temperature plays a role in the metabolism rate in fish. Different sites can have vastly different information. I keep my fish tanks at 75deg. To low and they become less active. Higher temps speed them up and ATM we don't want that.
Your fish are still young give them hides where they can get out of site and rest. They then can come out when they are ready to. This will lower their stress and help them. Floating plants real or fake can help them distress as well.