Hi everyone

I am planning on getting a tank somewhere around 125G. I am going to make this an oscar tank. Right now my plan is to purchase a single oscar and a group of silver dollars to go in with it as i have read that oscars do not tend to be aggressive toward silver dollar fish.

However, I am open to suggestions on some other types of tank mates. I'm really trying to avoid aggression as in my previous tank, aggression was an issue and it was really annoying. Any ideas?

Also, what type of gravel would be good for this tank? Would Onyx gravel be a good choice? It is said to have a slight buffering effect. Is this good for the fish?