Albino Oscar

They are the same species and they are establishing the pecking order/territories - are they close in size? Maybe rearrange the rock/decor in the tank - I often do that just before I add new fish - they should settle down - my oscars usually buddy up over time, but will have small fights here and there.

Oh boy...the size differential could be an issue - can you grow out the albino a little bit in another tank? If not, and the harassment continues, you may want to consider trading him in. Try the rock rearranging too, to see if that works.

I have quite a few oscars, and I had the same trouble when I bought a couple of 2 inchers and tried to keep them with my 6 inchers.

Just keep the smaller one in a seperate tank and power feed it for a few weeks and soon you'll be able to introduce it into the 100.

If you don't have an extra tank, see if you can find a larger albino and return the small one.

HTH,
Serg

Another thing you have to consider too is that your Oscar may not ever get along with another Oscar unless its for mating purposes and even then there can be problematic fish.... Even if they are OK around other species.
Oscars have such a wide ranges of personality,temper and aggression, from Mr. Niceguy to truly sociopathic and everything in-between.
Sometimes two O's can be best buddies for years and the next day you have to break'em up, there's just no telling with these fish sometimes.

Personally though from looking at your current stocking levels, this is probably purely territorial, your pretty well stocked with some aggressive fish.
One fish being the proverbial straw that broke the camels back.
I agree with trying to growout the Albino Oscar some more, and/or
re-arranging the tank decor to break up current territories.

IMHO, I'm surprised that with your Cichlid mix that you haven't already had some serious aggression/territorial issues.
Oscar, Midas, Jack Dempsey, Convict, African?

A little tip from personal experince. If you want an oscar to grow fast, try the floating Arrowana food made by Hikari. I switched from pelets to that and they blew up.