| Re: Stocking set up
If you really wanted to keep an oscar I would reccomend at least a 90 for 1... I know a lot of people keep them in 55's but there really isn't enough room for them to turn around in there, picture a 15" oscar trying to turn around in a tank that is 12" wide. You could probably keep it in there for about a year, depending on what you feed it, and how much.
IMO they are such dirty fish that I would go bare bottom, or large gravel, and in this rare case... maybe a good UG filter to suck all the crud up.
As for hiding places, personally I don't like the look of terracotta pots in a fish tank, and you probably won't really be able to get one big enough for an oscar in a 55. I would reccomend just digging up some large rocks from your back yard and putting them in the tank, which is what I did in my 90 for my SA cichlids, just make sure you put the rocks on the glass, or with a very thin layer of gravel around them so they can't be knocked over easily, try to get rocks with a wide base if possible. If you must stack, do something like a pyramid, larger rocks on the bottom and slowly build up into a corner or something.
Also make sure you weigh the top down, oscars are very powerful and if they jump, a plastic or glass hood by itsself is not going to stop it.
Just guessing here on the smallest species of oscar.... but if I had to guess, I would go with an albino red oscar, just because of the albanism, and the fact that it is bred to get the red color, not for size. On the other hand...every site, or book I have seen for oscars or sign in a store has said 15" I have also seen many 12-15" oscars, so it is a realistic size, compared to say... clown loaches getting 10 inches, very few people have the ability to keep a fish like that alive for long enough to reach their full size, and give them the right size tank, and all that, especially since they do much better in schools.
But anyways, I have also heard of oscars over that 15" mark.... however could just be fishing stories. | 
