I have had my oscar in a tank by himself since I got him around 2.5 years ago. He is in a 55gal I was wanting to know if anybody had some advice on what to add or if (since they are such territorial fish) I should add anything.
Wow no need to be so harsh. I bought the tank I bought after researching on the net, so many sites said 40gal minimum so I did what I thought I should and went bigger than that. I wasn't considering adding because I just wanted more fish I was worried about this fish, who is so close to my heart, being lonely. During those six days he turned blue and went belly up, so pardon my ignorance, I figured that near death experience must have harmed him somehow.His growth is NOT stunted from the snow days. Six days will NOT stunt a fish. However, 2.5 years in a tank that is too small will. Your Oscar should never have been in a 55 gallon tank. He should have been in a 75 as a minimum. Anyone that supports a 55 gallon doesn't know much about Oscars. They grow their entire lives unless in a tank that is too small. What happens is that a fish will secrete hormones that stops their growth. It does not effect their organs but effects the skeletal structure.
Your tank is way too short to house and Oscar. You need a minimum of 48" in length so it has room to swim.
Do not add any fish to the tank or further stunting will occur.